Not sure about the forward/reverse thing, but if your sled has electric start, a low battery can affect idling. And if you have a low idle, it can cause trouble with keeping the engine running when switching from forward/reverse. Because the battery is low, the stator is working extra hard to charge the battery putting excessive load in the engine at idle. This is especially present on a cold engine.
Although a lot of other factors can come into play such as engine temp, condition of the gas, clogged injectors ... and on and on. But battery charge is an easy one to check if your sled has one.