I've been having some odd issues with a Rapoo wireless mouse and keyboard (+usb dongle) on my PI 4. This combo has been used for a couple of years on a PI 3B+ with no issues.
Even with a new battery in the mouse I've been getting frequent mouse freezes (although the keyboard works). The only fix is to remove and re-insert the USB dongle which is pretty annoying
I have a fresh battery in the mouse and still getting freezes. I *suspect* it may be heat-related as those USB ports are getting really hot. I've got the dongle on a short extension cable now and so far its working well. PI 4 is mounted vertically with USB uppermost in free air.