What do i do if my game is stuck on a mod even after i do /set mod classic.tdm, How do i fix this?

First of all, it's .tbm and not .tdm.

Also, reinstalling should fix the problem. Report the bug to one of the game devs though.

Restart the game and/or the pc first! If that doesn't work, then reinstall is your best bet.

Restart the game, if that doesn't work Reinstall it, if that doesn't work Report the bug to the Devs.