Exactly as the title says. Starting the game in Forge 1.12.2 14.23.5.2838 fails, as MovingWorld causes it to crash, likely due to a change in the files accessed with the mixins. Unfortunately, it's before the game can generate a crash report, so I can't tell for sure.

Turns out I was wrong, it's actually a crash with Phosphor.

MovingWorld causes the crash because Phosphor tries to load Mixin 0.7.10 and MovingWorld has already loaded 0.7.8.