I have just updated to 5.5.2, created a new db and tried sync to cpanel webdisk. I got error first but tried again and clicked fast on sync button 5-6 times and finally it synced, verified data on the server, uploaded db file looks fine, but if I go into "tools/settings/sync/sync now" and try to sync again, it fails, I get this error below:
There went something wrong while synchronizing.
(Error: -117)
update: temporary installed NextCloud, this works well (most core contributors left ownCloud Inc and started a fork)