I think that I selected several files again to delete (which were already scheduled to be deleted) and deleted them, again it required admin rights and I moved it to the background.
Suddenly I got lots of "TCMADMIN.EXE" popups/msgbox-es informing me something went wrong -- see machine translation below -- and I had to close quite a lot of these (50 or so) which was quite tedious

Edit: TC11.51 32bit Windows 10machine translation so may not be accurate wrote:TCMADMIN.EXE - Delayed writes failed
Could not save all data for file [path]; data has been lost. This error may be caused by the device being removed or the media being write-protected.