Watch on office files not working

I’m trying to enable watch on office files, which are handled by Collabora.
When a user watches/modifies a file the watch function is not triggered, no notification.
Watch works good on folders and empty files.

Someone can help me?

Thank you

Cells v.4.0.1
Sys: Debian 11
Browser Opera desktop, Firefox desktop, Opera mobile, Firefox mobile

Anybody experiencing this?