I was using P-Slice (V-Slice; or Base Game and Psych Engine) and I accidentally got Tankman as a playable character and BF and Pico was locked and it said no mods were loaded.
Its a glitch when the game updates and loads into the protected github files i got it 2 times it will refuse to play tho just reset the game (btw can you explain which engine because you said psych and base game and according to me theres no mixed version and the glitch only works on v-slice)