Illustrator CC files keep on deleting themselves

I'm not a huge tech nerd, so excuse my inability to use correct terms. I've been using Illustrator and creative cloud for some years now for my work. Lately for unknown reasen ai.files have been "disappearing". They show in folders in gray and cannot be opened. If I go to the website of my cloud, I notice the missing files are in trash bin. But if I move them back, they soon get deleted again.

There are four people in my work group, but no one has deleted anything. The missing files are totally random, not the oldest or in any way unsimilar to anything I normally do.

Any ideas why this keeps on happening? Any suggestions to stop it?

Heli