C10 images dis- & reappear from selects folders

I noticed that C1 is not showing all of my images in the select folders. When I start C1 showing the specific selects folder, everything is fine.
If I browse trough other folders and then go back to the selects folder, some images are missing (one or two out of 36 for example). They will reappear when I restart C1.

I also lost my complete collection of select folders twice now. Luckily I had a catalogue backup.

Alex