Initial Case:
mdm and mdm-themes are installed.
lxdm was disabled (sudo systemctl disable lxdm)
mdm is enabled (sudo systemctl enable mdm)
Use Case:
At first login (after having (re)started my laptop) no issue is encountered.
From my DE (XFCE), I logout without any issue. MDM login screen is displayed again.
Issue:
Trying to login again always fails with authentication error message.
Workaround:
Clicking on the "Quit" button (if available in the mdm login screen) solves the issue: the mdm login screen seems to be repainted and login is correct.
Comment:
The workaround didn't work yesterday with the manjaro theme because the "quit" button wasn't available. It has been available since the update occured this morning.