Maps that shouldn't be lagging, but lagging anyway? Hm. Normally VX Ace runs pretty well, even with a lot of events and effects going on. (Though this does change when a ton of funky scripts are involved...)
I haven't looked at the data for the game myself, but I can only assume that somewhere there might be lag caused by a parallel event with a loop that doesn't have any wait frames. At the end of a parallel event there's a sort of implied wait frame, but if there's a loop then it never reaches the bottom of that event. Gotta manually place 1 wait frame yourself in those cases.
Viewing post in BUG FIX 1/KNOWN GLITCHES comments
To be honest, I'm really not sure what causes it? Some larger maps I can understand, but there's two specific smaller maps that no matter what I do just lag really badly, and I have no clue why? I'm guessing it's most likely a script that I'm using but I'm not sure which one. Thanks for the advice, I'll have to have a look and see if there's anything these two maps have in common, that I've just missed.