Sync larger than 18KiB files not possible with internal server error

I have a docker(official image) installation on my home server and have been using it for years.
(Nextcloud Hub 6 (27.1.1))

I don’t deal with large files, so I don’t do much with settings, and I’ve been syncing tens to hundreds of MiB files with no problems.
A few days ago, a 9.3MiB file failed to upload on my Mac client (v3.10.0), and since then I’ve been unable to sync from client to server.
Here’s what I’ve figured out so far.

  • (Important) Up to 17 KiB, synchronization works. From 18KiB, synchronization fails with a internal server error.
  • On the web, even larger files were uploadable. (However, even on a gigabit local network, uploading 1 MiB took tens of minutes)
  • Files already on the server are synced to the client without issue, regardless of size.
  • The problem is the same whether I’m at home or away.

Just to be on the safe side, I have all of the large file upload settings turned on, and I have the relevant settings turned on in the nginx proxy manager.

I’m also using Cloudflare, which I’ve been using for a few years now, so I don’t think it’s a problem, but I set the max chunk size to 10MiB just in case.

Spent whole two days with this problem.
This is a very painful situation because it was a useful tool to me.
Any help is welcome.

Some client logs below, “sync_test.txt” file size is 18KiB :

(Sorry for some Korean letters)

2023-09-26 10:05:39:841 [ info nextcloud.sync.engine /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncengine.cpp:774 ]:	#### Discovery end ####################################################  257 ms
2023-09-26 10:05:39:842 [ info nextcloud.sync.engine /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncengine.cpp:824 ]:	#### Reconcile (aboutToPropagate) ####################################################  258 ms
2023-09-26 10:05:39:842 [ info nextcloud.sync.statustracker /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncfilestatustracker.cpp:229 ]:	Investigating "sync_test.txt" OCC::SyncFileItem::NoStatus CSyncEnums::CSYNC_INSTRUCTION_NEW OCC::SyncFileItem::Up
2023-09-26 10:05:39:842 [ info nextcloud.sync.engine /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncengine.cpp:831 ]:	#### Reconcile (aboutToPropagate OK) ####################################################  258 ms
2023-09-26 10:05:39:843 [ info nextcloud.sync.engine /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncengine.cpp:885 ]:	#### Post-Reconcile end ####################################################  259 ms
2023-09-26 10:05:39:843 [ info nextcloud.gui.folder /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/folder.cpp:1150 ]:	#### Propagation start ####################################################
2023-09-26 10:05:39:844 [ info nextcloud.gui.application /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/owncloudgui.cpp:233 ]:	Sync state changed for folder  "https://my-nc-server/remote.php/dav/files/mash/" :  "Sync running"
2023-09-26 10:05:39:847 [ info nextcloud.sync.propagator.root.directory /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1457 ]:	scheduleSelfOrChild OCC::PropagatorJob::NotYetStarted pending uploads 0 subjobs state OCC::PropagatorJob::NotYetStarted
2023-09-26 10:05:39:847 [ warning nextcloud.sync.propagator.directory /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1208 ]:	Useless task found for file "sync_test.txt" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2023-09-26 10:05:39:847 [ info nextcloud.sync.propagator.root.directory /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1481 ]:	OCC::SyncFileItem::Success slotSubJobsFinished OCC::PropagatorJob::Running pending uploads 1 subjobs state OCC::PropagatorJob::Finished
2023-09-26 10:05:39:847 [ info nextcloud.sync.propagator /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1542 ]:	PropagateRootDirectory::scheduleDelayedJobs
2023-09-26 10:05:39:847 [ info nextcloud.sync.checksums /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/common/checksums.cpp:189 ]:	Computing "MD5" checksum of "/Users/mash/Nextcloud/sync_test.txt" in a thread
2023-09-26 10:05:39:848 [ info nextcloud.sync.propagator.bulkupload /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/bulkpropagatorjob.cpp:189 ]:	"/sync_test.txt" transmission checksum "f9debe3f07be68533bf0295e3d2ba68a" "/Users/mash/Nextcloud/sync_test.txt"
2023-09-26 10:05:39:849 [ info nextcloud.sync.accessmanager /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/accessmanager.cpp:78 ]:	4 "" "https://my-nc-server/remote.php/dav/bulk" has X-Request-ID "e190410e-f227-4cc8-80e8-9e9d5a6c455c"
2023-09-26 10:05:39:849 [ info nextcloud.sync.networkjob /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/abstractnetworkjob.cpp:363 ]:	OCC::PutMultiFileJob created for "https://my-nc-server" + "" "OCC::BulkPropagatorJob"
2023-09-26 10:05:39:949 [ info nextcloud.sync.credentials.webflow /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/creds/webflowcredentials.cpp:406 ]:	request finished
2023-09-26 10:05:39:949 [ warning nextcloud.sync.networkjob /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/abstractnetworkjob.cpp:221 ]:	QNetworkReply::InternalServerError "서버에서 \"POST https://my-nc-server/remote.php/dav/bulk\"에 \"500 Internal Server Error\"(으)로 응답함" QVariant(int, 500)
2023-09-26 10:05:39:949 [ warning nextcloud.sync.credentials.webflow /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/creds/webflowcredentials.cpp:208 ]:	QNetworkReply::InternalServerError
2023-09-26 10:05:39:950 [ warning nextcloud.sync.credentials.webflow /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/creds/webflowcredentials.cpp:209 ]:	"Error transferring https://my-nc-server/remote.php/dav/bulk - server replied: Internal Server Error"
2023-09-26 10:05:39:950 [ info nextcloud.sync.networkjob.put.multi /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/putmultifilejob.cpp:85 ]:	POST of "https://my-nc-server/remote.php/dav/bulk" "" FINISHED WITH STATUS "InternalServerError 서버에서 \"POST https://my-nc-server/remote.php/dav/bulk\"에 \"500 Internal Server Error\"(으)로 응답함" QVariant(int, 500) QVariant(QString, "Internal Server Error")
2023-09-26 10:05:39:950 [ warning nextcloud.sync.networkjob.put.multi /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "unknown error"
2023-09-26 10:05:39:950 [ info nextcloud.sync.propagator.bulkupload /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/bulkpropagatorjob.cpp:531 ]:	Item completed "sync_test.txt" OCC::SyncFileItem::NormalError CSyncEnums::CSYNC_INSTRUCTION_NEW "network error: 401"
2023-09-26 10:05:39:950 [ warning nextcloud.sync.propagator /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/bulkpropagatorjob.cpp:713 ]:	Could not complete propagation of "sync_test.txt" by OCC::BulkPropagatorJob(0x600000c7db00) with status OCC::SyncFileItem::NormalError and error: "network error: 401"
2023-09-26 10:05:39:950 [ info nextcloud.sync.propagator.bulkupload /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/bulkpropagatorjob.cpp:743 ]:	modify final status NormalError OCC::SyncFileItem::NormalError OCC::SyncFileItem::NormalError
2023-09-26 10:05:39:951 [ warning nextcloud.gui.activity /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/tray/usermodel.cpp:873 ]:	Item  "sync_test.txt"  retrieved resulted in  "network error: 401"
2023-09-26 10:05:39:951 [ warning nextcloud.gui.activity /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/tray/usermodel.cpp:835 ]:	Item  "sync_test.txt"  retrieved resulted in error  "network error: 401"
2023-09-26 10:05:39:951 [ info nextcloud.sync.propagator.bulkupload /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/bulkpropagatorjob.cpp:258 ]:	final status OCC::SyncFileItem::NormalError
2023-09-26 10:05:39:951 [ info nextcloud.sync.propagator.root.directory /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1481 ]:	OCC::SyncFileItem::NormalError slotSubJobsFinished OCC::PropagatorJob::Running pending uploads 0 subjobs state OCC::PropagatorJob::Finished
2023-09-26 10:05:39:951 [ info nextcloud.sync.propagator /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/owncloudpropagator.cpp:1497 ]:	PropagateRootDirectory::slotSubJobsFinished emit finished OCC::SyncFileItem::NormalError
2023-09-26 10:05:39:952 [ info nextcloud.sync.engine /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/libsync/syncengine.cpp:980 ]:	Sync run took  368 ms
2023-09-26 10:05:39:952 [ info nextcloud.gui.folder /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/folder.cpp:1157 ]:	Client version 3.10.0git (build 17671)  Qt 5.15.4  SSL  OpenSSL 1.1.1o  3 May 2022
2023-09-26 10:05:39:952 [ warning nextcloud.gui.folder /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/folder.cpp:1164 ]:	SyncEngine finished with ERROR
2023-09-26 10:05:39:953 [ debug com.nextcloud.owncloudgui /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/owncloudgui.cpp:410 ]	[ OCC::ownCloudGui::slotShowTrayMessage ]:	Going to show notification with title: ' "동기화 활동" ' and message: ' "sync_test.txt이 오류때문에 동기화되지 않았습니다. 자세한 내용은 로그를 참조하십시오." '
2023-09-26 10:05:39:953 [ info nextcloud.gui.folder /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/folder.cpp:411 ]:	Folder "" sync result:  OCC::SyncResult::SyncRunning
2023-09-26 10:05:39:953 [ info nextcloud.gui.folder /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/folder.cpp:1193 ]:	the last 1 syncs failed
2023-09-26 10:05:39:953 [ debug nextcloud.gui.macsystray /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/systray.mm:186 ]	[ OCC::checkNotificationAuth ]:	Authorization for notifications not granted.
2023-09-26 10:05:39:953 [ debug nextcloud.gui.macsystray /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/systray.mm:189 ]	[ OCC::checkNotificationAuth ]:	Error from notification center:  "Notifications are not allowed for this application"
2023-09-26 10:05:39:954 [ info nextcloud.gui.application /var/folders/yr/9dx0mtfj7kdf4725tmcz6md80000gp/T/macos-17671/src/gui/owncloudgui.cpp:233 ]:	Sync state changed for folder  "https://my-nc-server/remote.php/dav/files/mash/" :  "Error"

Thanks,