hi javou is the truck shut down and you get error 06 on the display
or just dont go forward to backward softly, error 06 is the servo motor
and going forward to backward too fast you need to adjust the plug braking, the higher the#the softly will take off, the lower # the faster will go, O! you also need had set to to adjust the plug braking, if you dont have one you need to call a fork lift service company
good luck,