Server responded with error when reading directory: operation aborted

Nextcloud version (eg, 20.0.5): 3.5.1
Operating system and version (eg, Ubuntu 20.04): Windows 11

Sync is failing because of the error message “server responded with an error while reading directory “…”: operation aborted” (translated from German, might be slightly incorrect)

The status window shows no details at all:

The settings window shows the above mentioned error:

The client log has no error messages. Only a few warnings:

2022-05-25 09:59:26:932 [ warning nextcloud.sync.networkjob.jsonapi C:\Users\sysadmin\AppData\Local\Temp\2\windows-10303\client-building\desktop\src\libsync\networkjobs.cpp:903 ]:	Nothing changed so nothing to retrieve - status code:  304
2022-05-25 09:59:26:932 [ warning nextcloud.gui.servernotification C:\Users\sysadmin\AppData\Local\Temp\2\windows-10303\client-building\desktop\src\gui\tray\notificationhandler.cpp:73 ]:	Status code  304  Not Modified - No new notifications.
2022-05-25 09:59:34:286 [ warning nextcloud.sync.networkjob C:\Users\sysadmin\AppData\Local\Temp\2\windows-10303\client-building\desktop\src\libsync\abstractnetworkjob.cpp:224 ]:	QNetworkReply::ContentNotFoundError "Server hat \"404 Not Found\" auf \"GET xxxx/avatars/xxxx/128.png\" geantwortet" QVariant(int, 404)
2022-05-25 09:59:34:286 [ warning nextcloud.sync.credentials.webflow C:\Users\sysadmin\AppData\Local\Temp\2\windows-10303\client-building\desktop\src\gui\creds\webflowcredentials.cpp:227 ]:	QNetworkReply::ContentNotFoundError
2022-05-25 09:59:34:286 [ warning nextcloud.sync.credentials.webflow C:\Users\sysadmin\AppData\Local\Temp\2\windows-10303\client-building\desktop\src\gui\creds\webflowcredentials.cpp:228 ]:	"Error transferring hxxxxx/avatars/xxxxx/128.png - server replied: Not Found"

The server log shows an unknown error

{"reqId":"xxxxx","level":3,"time":"2022-05-25T07:22:19+00:00","remoteAddr":"xxxxx","user":"xxxxx","app":"PHP","method":"GET","url":"/ocs/v2.php/apps/notifications/api/v2/notifications?format=json","message":"OC\\DB\\Exceptions\\DbalException: An exception occurred while executing a query: SQLSTATE[70100]: <<Unknown error>>: 1927 Connection was killed at /var/www/html/lib/private/DB/Exceptions/DbalException.php#71","userAgent":"Mozilla/5.0 (Windows) mirall/3.5.1stable-Win64 (build 20220517) (Nextcloud, windows-10.0.22000 ClientArchitecture: x86_64 OsArchitecture: x86_64)","version":""}

The error must be with the client, as I have a linux machine which is syncing fine and all other users of the nextcloud server have no issues. Only this one windows machine is having this issue. I want to avoid deleting the sync and resyncing, as there are local changes I don’t want to manually search and save, and the share is >500GB which takes ages syncing from scratch.