I'm getting this now when I load a map. Even when this and its libraries are the only mods. Weird because it worked fine before

The mod Multiple Unit Train Control (0.4.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event MultipleUnitTrainControl::on_init()
Can't register 0th tick.
stack traceback:
[C]: in function 'on_nth_tick'
MultipleUnitTrainControl/control.lua:313: in function 'StartTrainWatcher'
MultipleUnitTrainControl/control.lua:644: in function 'init_events'
MultipleUnitTrainControl/control.lua:708: in function <MultipleUnitTrainControl/control.lua:700>

You have fuel rebalancing disabled (settings_nth_tick=0), and the new code I added for compatibility with Renai Transportation forgot to check that. Thanks for the report. A new release will be out shortly.