Activating MUTC (replaces all locomotives) while this mod is active results in the following crash:

Error while running event howfardiditgo::on_nth_tick(30)
LuaTrain API call when LuaTrain was invalid.
stack traceback:
    __howfardiditgo__/control.lua:68: in function <__howfardiditgo__/control.lua:65>
stack traceback:
    [C]: in function '__index'
    __howfardiditgo__/control.lua:68: in function <__howfardiditgo__/control.lua:65>

Thanks, at the moment non-vanilla types of carriage aren't supported, so I'll look into incompatibilities like this as and when they come up and update when it's fixed.

Thanks
Jack

This is (finally) fixed in 0.17.5.

Unfortunately when the trains get swapped to the new locomotives, the distances get wiped. So far I've not thought of a way around it, but maybe in another 5 months I'll come up with something ;)

All you have to do is store distances in a train id indexed table.
Then migrate ids in https://lua-api.factorio.com/latest/events.html#on_train_created

This is already what this mod does. Without MUT it works fine. My guess is the data is being cleared prematurely when MUT updates the locomotives, but I need to look into it more