I'm running Joplin 1.0.312 on Android 9 and on Win10 it's Joplin 1.0.175. I have 1000+ notes stored and the setup has been working well for quite a few months. Syncing via Nextcloud and also using encryption.
Unfortunately about a week ago, the Android app stopped decrypting new notes that were created on the Windows machine.
I ran a backup on Windows, deleted all the data files on both Android and Windows and imported the backup on Windows. Enabled encryption there and then the sync to Nextcloud. Once all the files had been uploaded I connected the Android app to Nextcloud to run the sync. Which seemed to work just fine. Eventually the Masterkey arrived but I still waited for the sync to finish before I entered it. Then the decryption process started and it all seemed to work just fine. A lot of files got decrypted. But then it suddenly just stoped. I gave it a day or two but nothing is happening. Also the counter for the files being processed disappeared. I assume it has to do with the error messages in the log file. Joplin seems to keep trying but that's where it stops:
01-13T01:52:42,10,"""DecryptionWorker:", "{"message":"Row too big to fit into CursorWindow requiredPos=43, totalRows=44","code":0}""
Here's the complete log file:
syncReport-1578933521780.txt (1.7 MB)
Another thought. I am using the webclipper a lot on Windows. My guess is, that this is where the problem starts. Creating parts of the files that are too big or in any way incompatible.
Hope you can help. I'd hate to disable the encryption. Matter of principle 
Cheers,
Peter