The problem seems to be related to having multiple displays.

In Stretch+TDE-r14.0.5 I had two displays on one NVidia adaptor,
not combined, with TDE only using the primary display.

After migrating to Buster+TDE-14.0.7(PSB) the display crashed
multiple times per second after logging in, giving the appearance
of flashing like crazy.  However TDM and Failsafe mode worked fine.

After running RandR in global mode from Systray, TDE once again
works without crashing but RandR cannot see the second display,
neither initially nor after rescanning displays.

In r14.0.5 RandR could see the second display and asked me whether
or not I wanted to include it in TDE.

However the second display works fine in X because I can start
Factorio from TDE and direct it to run on the second display.

I don't think there's enough specifics here to file a bug yet.
Let me know if there's more I can do to help.

--Mike