This is just to let you know that the workaround reported by John Franklin on 22 June works for me too.
That is, since adding this *.conf file, I haven't seen the buggy behaviour anymore:
/etc/X11/xorg.conf.d/20-intel.conf
Section "Device"
Identifier "Intel Graphics"
Driver "intel"
EndSection
I'm running a fresh install of Buster with XFCE (xfce4 + goodies) on a Thinkpad X220 (Intel HD 3000 graphics).
I hope it helps at least a little in isolating the problem.