not sure if this is still true
the old machines used to have a hot and cold valve. the hot valve had to work on lower pressures as a lot of houses had pressure from the loft storage tank. the only difference between the 2 valve was a pressure control device on the entrance to the valve. It wasnt so much of a pressure device but more of a volume reduction device. it consisted of a rubber washer that would close over more and more if the flow increased
take the inlet hose off your machine, carefully remove the water filter from the valve entrance. look behind this valve and see if there is a rubber washer. If yes remove it and replace filter and try it
Dave