I'll investigate it but the thing is you don't suppose to have trains in the game that this mod would change. The mod is only meant to be installed before you'd place/use any of the t2-t4 train machinery, otherwise all wagons will be broken (in terms of their collision boxes, connection points, etc) and won't function properly (there's no fix for this, this is just how the game works - trains need to be deconstructed and put back again to apply the changes that this mod makes). There's a high chance that the UPS tax is connected to that fact.
