Trailers are duplicating on travel the duplicated trailer is left in the previous location as if it were detached before traveling. the cargo is duplicated as well.
could you be more specific on where did this happen and with what truck/trailer? so we can try do duplicate.
so far every time I go thru a gate with a trailer. all four maps on Alaska and Michigan. all trailers seem to do this. Though I haven't tried an oversized event trailer.
as far as what trucks it seems to be any as well. scout trailers do this as well. i'm still playing thru and the only way I can stop this duplication is to wench to the trailer before travel.