You sure you are not missing a "0" in that platform number? In any case, now is the time to get to know the innards of your RC, and how they work.
Perhaps a pin(s) is busted inside the diff, or the screws have come loose. Instruction manual/parts diagram by your side... get in there and investigate.
The following is from the 144001 manual...
The screws that are circled is where I'd check first.