Desktop clients deleted files on its own

Hi all,
This morning I turned my portable pc on and nextcloud client (version 2.3.3 running on ArchLinux) showed me a notification about deleted files.

Since I did not delete anything from last time I turned my portable PC on, I immediatley checked what files have been deleted. The files are gone from my portable pc indeed!! I did not delete them, they are not shared. Luckily, they are still there on my desktop PC and I can still see them on the web interface.

What happened? This is horrible! Files should never disappear like this. How can I be sure this deletion will not propagate to the server and other nextcloud clients?

Please, help me figuring out what happened.