Ashley - Thanks. I've emailed you a dropbox link for my capx file. You're likely right that it's a fillrate issue, however , my layout size is 4500, 2000 (resolution is 640 x 360). I'm using 4 layers that each have a tilemap on it (3 are the same file, 1 is a collision tilemap), and I do have 1 layer that is set to force texture with maybe 20-30 sprites that have destination out on it. I'm also using maybe 10-20 sprites that have the additive blend mode.
If those are truly what's causing the problem, to ME that literally means that using tilemaps or any blend modes in general should be prohibited for anything that isn't a flappy bird or mario-type game.
Ironically enough, when I deleted all of my "light" with destination out sprites, it didn't actually help anything.
— - Unfortunately, no. It's pixel art with almost nothing having any behaviors or effects. The particular layout is 1 enemy that has no events to it, and I've disabled the groups for all other enemies. I'm not using super heavy fx, or any large objects. Most sprites are either a tilemap or static.