Hello! I'm having some trouble regarding a D12 pallet stacker ( i think thats the right term). Anyways, after stacking a lot of pallets high and low, it suddenly doesn't want to go fast as usual, just in slow mode, just like when the forks or body are lifted. I suppose its a fork sensor thing? Already tried discinnecting it, and shorting the contacts but no help there. All the cells are equal in voltage.