Nextcloud desktop crashes when uploading more than about 1MB of files

I’ve recently been having issues with the nextcloud desktop client immediately crashing if it has to sync more than about 2MB of files at once. As soon as it needs to sync more files than some threshold around 2MB, the client immediately crashes.

OS: Kubuntu 24.04
Self-hosted Nextcloud Hub 8 (29.0.2) on Hostinger shared web hosting.
Reproducable with AppImage 3.12.5, 3.13.0 and PPA-installed 3.13.0 versions of the desktop client.

I made a client log file of a session where I slowly added larger and larger batches of files to my synced folder until the client crashed. I couldn’t see any obvious errors. These lines looked a little suspicious, but occurred earlier in the job when syncing was still working:

2024-06-10 18:54:58:082 [ warning nextcloud.sync.propagator.directory ./src/libsync/owncloudpropagator.cpp:1267 ]:	Useless task found for file "Wilde Kapelle/Altländer Nr. 31.pdf" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2024-06-10 18:54:59:767 [ warning nextcloud.sync.networkjob.put.multi ./src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "Unknown error"
2024-06-10 18:55:12:234 [ warning nextcloud.sync.networkjob.put.multi ./src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "Unknown error"
2024-06-10 18:55:12:234 [ warning nextcloud.sync.networkjob.put.multi ./src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "Unknown error"
2024-06-10 18:55:12:234 [ warning nextcloud.sync.networkjob.put.multi ./src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "Unknown error"
2024-06-10 18:55:12:234 [ warning nextcloud.sync.networkjob.put.multi ./src/libsync/putmultifilejob.cpp:94 ]:	oneDevice has error: "Unknown error"
2024-06-10 18:55:12:234 [ warning nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:419 ]:	Server does not support X-OC-MTime ""

These are the last lines before the app crashed and stopped writing to the log file:

2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.root.directory ./src/libsync/owncloudpropagator.cpp:1588 ]:	scheduleSelfOrChild OCC::PropagatorJob::Running pending uploads 3 subjobs state OCC::PropagatorJob::Running
2024-06-10 18:55:40:012 [ warning nextcloud.sync.propagator.directory ./src/libsync/owncloudpropagator.cpp:1267 ]:	Useless task found for file "Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes Text.pdf" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2024-06-10 18:55:40:012 [ warning nextcloud.sync.propagator.directory ./src/libsync/owncloudpropagator.cpp:1267 ]:	Useless task found for file "Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.ogg" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2024-06-10 18:55:40:012 [ warning nextcloud.sync.propagator.directory ./src/libsync/owncloudpropagator.cpp:1267 ]:	Useless task found for file "Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.pdf" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2024-06-10 18:55:40:012 [ warning nextcloud.sync.propagator.directory ./src/libsync/owncloudpropagator.cpp:1267 ]:	Useless task found for file "Wilde Kapelle/Figaro.ogg" instruction CSyncEnums::CSYNC_INSTRUCTION_NEW
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.root.directory ./src/libsync/owncloudpropagator.cpp:1612 ]:	OCC::SyncFileItem::Success slotSubJobsFinished OCC::PropagatorJob::Running pending uploads 7 subjobs state OCC::PropagatorJob::Finished
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator ./src/libsync/owncloudpropagator.cpp:1673 ]:	PropagateRootDirectory::scheduleDelayedJobs
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter Text.pdf" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter.ogg" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter.pdf" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes Text.pdf" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.ogg" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.pdf" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.checksums ./src/common/checksums.cpp:204 ]:	Computing "MD5" checksum of "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Figaro.ogg" in a thread
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Der Schnitter Text.pdf" transmission checksum "2233d79a9d7e10aaa3783ef8888899be" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter Text.pdf"
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Der Schnitter.pdf" transmission checksum "2233d79a9d7e10aaa3783ef8888899be" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter.pdf"
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes Text.pdf" transmission checksum "1b67ed8177eced194395f9e363a4f3b2" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes Text.pdf"
2024-06-10 18:55:40:012 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.pdf" transmission checksum "1b67ed8177eced194395f9e363a4f3b2" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.pdf"
2024-06-10 18:55:40:013 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Der Schnitter.ogg" transmission checksum "d7db4eb4975c5344d268405f625f7374" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Der Schnitter.ogg"
2024-06-10 18:55:40:013 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Figaro.ogg" transmission checksum "303a7e88a4d5ca3a8a23400912a651cc" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Figaro.ogg"
2024-06-10 18:55:40:013 [ info nextcloud.sync.propagator.bulkupload ./src/libsync/bulkpropagatorjob.cpp:189 ]:	"/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.ogg" transmission checksum "4ec5e7ee8dde2ab31ff330884e706422" "/home/barnaby/Nextcloud/cloud.waterpigs.co.uk/Wilde Kapelle/Die Beschwerlichkeiten des Ehestandes.ogg"
2024-06-10 18:55:40:013 [ info nextcloud.sync.accessmanager ./src/libsync/accessmanager.cpp:78 ]:	4 "" "https://cloud.waterpigs.co.uk/remote.php/dav/bulk" has X-Request-ID "ca0f556d-e4ad-45e5-95ef-d8dd1bfb628b"

I cleared out my nextcloud folder and recreated the absolutely essential folders by slowly drip-feeding files into it, but I don‘t see any way of continuing to use nextcloud while this problem persists. Any ideas what might be causing it, or how to debug it more thoroughly?

What are the physical devices that your client computer goes thru for the internet?

Just a FritzBox 7530 router. I restarted it and nextcloud now appears to be working slightly better – it managed to sync a 10MB batch of files, but still choked on a 120MB batch. So, better than nothing, but still not ideal.

Just to sanity check things: What happens when you upload files via the Web UI instead of the Desktop client?

Try setting Prioritization in the router https://en.avm.de/service/knowledge-base/dok/FRITZ-Box-7530/228_Prioritizing-internet-access-for-important-network-applications-and-devices-in-the-FRITZ-Box/
for the category or network applications DNS or port 53, http or port 80 and https or port 443.

Hope that helps.