Sync on Android phone aborts with Error: PUT, Exception 400

I am using Joplin with Nextcloud synchronisation on my Windows PC (version 1.0.245), my Ubuntu laptop (version 1.0.245) and on my Android Phone (version 1.0.339) since about a year without any problems.

Yesterday I did update my Nextcloud server (Raspberey Pi) to version 19.0.3.
After that I realized, that the Joplin app on my Android phone did change synchronisation target fron Nexcloud to Dropbox wihtout any interaction by me.
After I did change it back to Nextcloud the synchronisation does not work any more.
I always get the error:

Error: PUT .resource/43c6024a0d30420888b5e59d7af2ce8b: Expected filesize of 64681 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 8192 bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side. (Exception Sabre\DAV\Exception\BadRequest) (400): <?xml version="1.0" encoding="utf-8"?>
<d:error xmlns:d="DAV:" xmlns:s="http://sabredav.org/ns">
<s:exception>Sabre\DAV\Exception\BadRequest</s:exception>
<s:message>Expected filesize of 64681 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 8192 bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side.</s:message>
</d:error>

To resolve this issue I first did reboot my Nextcloud server without any effect.
After that I did uninstall the Joplin app on my phone (after deleting all data) and did a reinstall of the app.
But the effect did not change, only all my notes on the phone were lost.
When I tried to find the file mentioned in the error message (.resource/43c6024a0d30420888b5e59d7af2ce8b) I did realize, that it does not exist on my Nextcloud server.

The Joplin installations on my PC and on my laptop do still not have any issue, they work as expected without any issue.

Does anybodfy has a hint what could go wrong on my smartphone?
I mainly started using Joplin to have my notes alvailable when I am out of home.

Thanks in advance and best regards,
Andreas

P.S. I found this issue: Appended files not synchronized, but in my case, no encryption is activated.

In addition I did the following test:
I created a new folder "test" on my Nextcloud server and did change the synchronisation path in the Joplin app to this.
Although no old files could be in that folder, the same error occurs. It is always "Expected filesize of 64681 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 8192 bytes."

In between I did another test that runs me crazy:

I did install the Joplin Android App on another smartphone and I did use another Nextcloud user for syncronization.
But I still the same error occurs:

Error: PUT .resource/43c6024a0d30420888b5e59d7af2ce8b: Expected filesize of 64681 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 8192 bytes.

Just the ID of the resource does change.
This means, the Joplin files on my Nextcloud server cannot be the root cause as they belong to another user.

What could be the issue?
What is behind the error message? Does it mean, the JoplinApp on my phone has created a resource that cannot be syncronized to my Nextcloud server?
And why does this happen?

Thanks in advance and best regards,
Andreas

Finally I solved the issue by a new installation of my NextCloud server.
It seems that the update of NextCloud to version 19.0.3 resulted in that problem, but I have really no idea what went wrong.
Neverthelesss it is not an issue fo Joplin!.

Was it a problem with 19.0.3 or just with the upgrade? What about 19.0.4?

There was an issue with 19.0.0 that was fixed in 19.0.1, but it seems that Nextcloud has broken WebDAV quite a few times now. Not sure how their QA process looks like. Oh, the main functionality for sharing and accessing files is broken, but let's release it anyway.

Usually when something like this happens, it's always the server's fault. Some do not follow RFC specs, some do their own thing, it's hard to keep track of all those things.

After the new installation of my NextCloud server Joplin was functional again although the version of NextCloud was still 19.0.3.
Therefore it seems that it was an issue with the upgrade itself.