So, i was going to play some modded mm8bdm but then i noticed all my data was erased (prob) and the transitions are the old doom transitions.

what do i do?

Back up your data for next time and either play the entire game legit or be like Billy Mitchell and play the game "legit"

it worked! (i forgor to send the message for over a year idk how)

Moving this thread to closed then. In general, issues potentially related to mod use shouldn't be reported here. It's best if you reach out to the creators of that mod to see if there's anything their mod could be doing that'd cause the interference.