Wow, my sentence parsing is horrid. Sorry about that.
Yep, v51 doesn't suffer from the same hangs. It might be something to do with compositing, or the like, as adjusting opacity/strength of a layer also causes more stuttering/slow downs than previous.
Sorry, spot on, meant the spec/gloss rather than the normal layers.
As an aside, I've definitely noticed the hang as well. Unsure re. older VAM version.