Raspberry Pi4 2gb - after updating adding Cairo Dock- not able to log into DE

Raspberry Pi 4 2gb- Mate 20.04.1 64bit - after updating adding Cairo Dock- not able to log in DE
Not sure if this is a problem with vanilla Mate out of the box or because I install Cairo Dock. It's one of the first things I do after updating.
After reboot, I have MATE or Cairo Dock DE to choose from at logon. Any selection seems to go in/ then back out to logon screen. Never able to get back into system anymore.
This has happened 2X now, after starting from scratch.

Anyone else see this?