System freezes for a few seconds when pressing certain keys Xubuntu 20.04

After having used my computer for a few days, it started to freeze occasionally for a few seconds when I pressed certain buttons. Even when this started to happen I was not able figure out how to reproduce this phenomenon reliably. It seems to me that this was more likely to happen when I pressed keys (or combination of keys) to which certain tasks were assigned (like brightness keys or shortcuts). Also it always happened once for each button. (So for instance I pressed the mute key then it froze but after that I didn’t freeze when I pressed it again.)

Logging out and logging in again resolves the issue (no reboot needed). I only experienced this problem in the XFCE environment, but I don’t know if this bug is specific to it.