Mouse starts jumping wildly on guest desktop

Sometimes mouse goes completely crazy and starts jumping around the guest desktop by itself and becomes completely unusable.

This does not happen on every boot, only sometimes. It may be caused by some input combination but I haven't yet found any specific cause. It happens soon after the desktop has been loaded and rebooting seems to be the only way to resolve the situation.


Guest: Kubuntu 20.04 64-bit (live), with KDE desktop
Host: Arch Linux, with KDE desktop
QEMU version: 5.1.0

QEMU start command:
qemu-system-x86_64 -enable-kvm -m 6G -cpu host -smp 3 -cdrom ./linux/kubuntu-20.04-desktop-amd64.iso -boot d -vga virtio -soundhw hda -display sdl,gl=on