I switch on welder pp256, set amp to 115, preflow to 1sec,up and downslope,end amps to 45,start to weld ok press switch to stop slops down and stops weld,but the gas is still flowing I have to turn bottle off,also the amps show 45 not 115,and will not adjust,any help out there,the welder is only one month old,iam in uk cheers mick