I don't have any problems with the normal maps but the latest reworked maps painfully drop my framerate. My PC is not very well but since it works just fine on older maps, i wondered why not on reworked ones. I play on low graphics as well.
Reworked maps have highly detailed textures, meshes, models etc. which causes more job to handle for your GPU or CPU. Some old maps run with the old assets that's why you're getting more stable frames.
dang. is there a way that i could solve the fps drop a little? for example playing in windowed always helped me reduce the drop, so maybe something like that?