Unfortunately X11 isn't without issues as well. In my case Wayland runs smoother and is less error prone than X11.

Can you confirm that it's only the taskbar that freezes? Do any other DE components (e.g. app launcher (shortcut meta + f2 by default)) work or do they freeze/not respond as well?

You could check various logs for errors:

• syslog (/var/log/syslog or dmesg)
• unit files of Plasma components (journalctl -xeu $UNITNAME; e.g. journalctl -xeu sddm.service)