I have a 2000series walkie pallet jack with a model number of wp2030-45 type E and a serial number of 5A320573. When I use the pallet jack everthing works fine and holds a charge but sometimes when I go to raise and lower a pallet jack with a load it will flash a yellow and green light at the same time and only blink once, and will not allow me to go forward or reverse but will let me lower or raise after the lights have flashed. in order the reset this i have to turn off the pallet jack and turn it back on. the same lights will flash only once everytime I hit the raise or lower button. Please Help!!