okay, I've narrow it down to be marco, marco 1.26.1 seem to cause this issue, downgrade it to 1.26.0 then MATE works fine again. Could you verify that by install libmarco-private2 from 15.4 or somewhere else if version 1.26.0, or you can get it from https://download.opensuse.org/repositories/home:/mlin7442:/rebuild_mate/openSUSE_Leap_15.5/ I will do a version revert towards marco in Leap 15.5.