Bridge shows photos in collection twice and more

I've a collection in Bridge with about 3000 photos in it. (Windows 10, Brdige 11.0.1)
If I copy a photo (CTRL+C) and paste it e.g. into anohter folder and came back to the Bridge's window with the collection, every photo is shown twice. If I again copy another photo and come back, every photo in the collection is no third times there.

If I change to another collection and switch back to the original one, everything is fine. And starts from the beginning if I again copy a photo.

This is an behaviour that I observe in Bridge for many years back until late 2010.

I'm wondering what this is and why this bug never was fixed in 11 years.