The issue is caused by WebDav server from somewhere around version 2.4.0.
Based on my discussion with Synology support, for solving some issue with not able to overwrite file even when one have user write file permission:
our developer adjust the mechanism while uploading files, it will call the SYNOACLPermCheck to check the permission, but it will have problem if the shared folder is in Linux mode.
They suggest me to turn ACL permission on for the share, but my share was home directory and I didn't want it on it. So I have created new share, turn ACL permission on it.
- I then turn off sync of notes in joplin on all my clients.
- Copied files using shell from original location to this new location.
- Change location of sync in one of the client to test
Now it is running the sync fine. I also see that lock is overwritten without issue every few minutes (and it was failing on it - on every overwrite).
I think I can say this solution is working.
Synology NAS on DSM 6; WebDav server 2.4.1.0108 client on windows and linux and android (even last two are not tested yet, but I assume there will no be issue as the problem was not joplin app/client related)
Thank you all for suggestions and help
-richo-