I am using Cubase 10.5.12. I have a project with many audio tracks, and a few VST instrument tracks. It has my cpu maxed out, and it often will not play with all the plugins enabled.
However, by selecting one of the instrument tracks as the “currently selected track”, Cubase will sometimes go ahead and play the project, depending on whether I have certain plugins disabled or not.
I have been able to continue working on this project, adding plugins where needed, etc., as long as I sit on a VST instrument track. Some VST instrument tracks may work better for this trick than others.