I've been having some issues as well, but I was assuming "dropouts" (which may be a fairly vague term) was something with my audio interface, I froze tracks, archived tracks, streamlined plugins, and adjusted ASIO latency, didn't help. Granted, my current project is surely pushed to the max with plugins, but then I adjusted my midi playback buffers. I did this as a last resort and it actually worked for me.
I haven't had to adjust my midi playback buffers since I can't remember when . . . it's always been at 750 msec, for many years. Moving it up to 1000 msec buffers solved it for me.
I'm not saying this is the same case for everyone here, but somehow this latest Platinum update has changed something with my midi buffer requirements ? Just something else to try, if nothing else works for your projects.
And, yes . . . I've been blaming the new Adaptive Limiter as the possible cause for this . . . but switching back to Concrete Limiter, the issues persisted. By adjusting my midi buffers, I'm also able to run Adaptive Limiter in this crazy project, successfully.