Xwayland bad cursor positioning after displayport monitor hotplug

My setup:

• Left monitor, 2560x1440 DVI (primary monitor)
• Right monitor, 1920x1200 DisplayPort
• Debian Buster amd64, Xwayland 1.20.4, Kwin_wayland 5.14.5

Steps to reproduce:

1. Use PC normally
2. Open an XWayland app (e.g. Chromium) on left monitor, interact with it normally
3. Turn off right-monitor.
   • For DisplayPort this causes a hotplug event, all open windows move to the left monitor, kwin "compositor settings" window pops up
4. Turn on right-monitor.
   • Open windows move back

Expected behavior:

• Expected to still be able to interact with XWayland apps normally

What goes wrong:

• Mouse input on all xwayland apps on left monitor is not properly recognized.
  • Some input is recognized, but, with a bad relative offset. Or it's only recognized outside of a 1920x1200 region on the 2560x1440 display
  • This includes click events being misdirected to wrong parts of the window, it affects dragging window, it affects mouse-hover on UI elements etc

Native wayland apps (Qt QML-based, ...) are not affected and can be used normally on both screens after the hotplug event.

Xwayland apps work fine when moved back to the right-hand monitor (e.g by alt-drag, since dragging on window decoration is unreliable) and repeatably stop working fine when moved back to the left-hand monitor

I am reporting this as an XWayland bug because it seems like only apps running under xwayland are affected,