“Other items” in icloud photos

Hi

i see that there is another category (other than photo and video) called “other items” in iCloud photos ?

firstly, what are these ?

secondly, could this be causing a problem in icloud syncing and leaving shared library (all my devices are stuck) at the same point in icloud syncing. I can neither exit nor go back to shared library

how to delete them

third, is there a way to delete these “other items”