I hope this is the right place to post this incident!
Looks like a couple of files in the “notes” directory got deleted and therefore got lost on my Nextcloud server after upgrading “notes” to 4.8.1 (Nextcloud server version at that time 27.0.0). I did not find any common characteristic of these files. They were also placed in different sub-directories under “notes”.
Fortunatelly I have a regular version-controlled backup on my laptop running the Nextcloud desktop client. This just happend once so far.
I am also using the “notes” app on my Android phone. So I wonder if this also could be the culprit.
Did anyone else observe something similar so far?