Solved my problem. It was the WorldEdit CUI mod that was causing the problem.
I found a different WorldEdit CUI Forge edition download here that worked. The first one I tried also said it was 1.11 Forge edition, but it didn't launch with Replay Mod.
If you only want to run WorldEdit and Replay Mod on their own, the download page for WorldEdit can be found here.
Combined with the above CUI mod, everything launches great! If I run into any further problems after testing, I'll let you know.
Cheers!