I'm trying to practice for a Nightmare run of Episode 1. I wanted to practice each level individually and made saves for M3-8. However, when I load these saves, enemies seem slower than normal. Is there a way to fix this?

Unfortunately, there's no real way to "fix" this, and your best bet is to just avoid using saves on Nightmare difficulty. This is a known issue and it's best to just freshly load into the maps via the main menu if you wish to play them on Nightmare.

Ok, thanks for the quick reply.