I now have a project that when closed, will not go away.
 
All I have to do is open the project and close it. The close dialog seems to start to close, but then X2 freezes and goes to the dubious white screen of death for Cakewalk.
 
When the project opens, I get a message that transients are being built. I don't know if that has anything to do with it, but clearly the host should not white screen and freeze.

Just tried to open, edit and close the project in 8.5 - No issue encountered. I can reproduce the white screen in X2 100% of the time with this project.

I may just stay with 8.5 for a while and seriously think about upgrading to any 'X' version in the near future.

I had a similar problem porting an X1 project into X2.
It turned out to be IK's SVX plugin.
In X2 I could open the project and play it once.
X2a would crash (white screen) every time I tried to open the project.
Any of the ik plugs that have not been updated in recent memory crash X2 for me.
You've got a plug that X2 doesn't like.

T

The only plugs I have are Waves plugs. I will report this to Waves also.

BTW - this opens and closes fine in X1 without issue.

have you opened/closed it in safe mode?.. seems like something is getting hung and its usually some plug of some description