This is an two-faced issue I think. When I am making an orchestral score with lots and lots of VST instruments at some point there seems to be a disconnect in the VST instruments table causing the file to load, but the audio engine to be dead (greyed out play button, forever (i have waited)). I could have 28 instances of Kontakt/BBC Orchestra plus one Halion and everything is OK, but then somewhere after adding another halion instance the thing does not load. Moreover if I clear VST slot to ----- I cannot delete it, and cannot make adjustments in the left player sidebar. All added VST are VST3.0, and all other VST are blacklisted by me. Why You ask?
I have noticed similar behaviour when adding VST2.0 instruments to the pile. After adding f.eg. UVI Workstation or sampler like TX16WX the same happens, even with small files. Instruments are referencing wrong slot number in VST instrument table (if they say they reference 4, they actually send midi to fifth or more) and the lower, bugged slots are impossible to delete. I think I wrote about this, but now I cannot find it.
I tried to search the forum and found no solution to this. If there is one, or the problem is known, I apologise.
I have observed similar behaviour on two machines - my Apple macbook, and my beastly Hackintosh with 32gb ram and 4,2 GHz Intel Core i7.
All the best, Nikola