Jumping menubar in newly installed PureOS as HVM in QubesOS

I’ve just installed the latest PureOS 8.0 as a HVM in QubesOS 3.2. The install wen’t fine, but when logging in, the menu bar jumps from top to bottom, hysterically(several times a second), when moving mouse or typing.

Anyone knows of a way to force the bar to stay put?

Sincerely
Max