Hi, This issue appears to be a duplicate of the widespread Mesa bug from late 2022 / early 2023, where KWin crashed with "The X11 connection broke: I/O error (code 1)" during notification popups.
The root cause was tracked down to Mesa and fixed upstream in Mesa 22.3.0 (reverting problematic commits). The same issue was tracked on Launchpad as bug #2003339. Since the underlying graphics driver bug has been resolved for a long time, this kwin-x11 ticket can probably be closed.
