problem running X on recent Debian

I have difficulties running Xorg on the recent debian (11.0). When I start X with startx or xinit (this is minimum embedded system); the X window drops after a few seconds. However, if I remove .xsession, X works ok (with default WM). Even, if the .xsession is empty or contain only commands the X drops. All previous debian versions including recent testing versions worked as expected. Only I have trouble with the recent stable version. No evident error was logged in either Xorg.log or .xsession-errors.
Questions:
Is .xsession deprecated?
Or there is possible bug in the recent stable version.
I would appreciate any comment.