Simpson 22S700 doesn't always fill with water?

For some reason the cold water pressure gets lost and doesn't fill the machine (only drbibles in). No issue with a hot water fill. If I turn the tap off at the wall and turn it back on (sometimes several times), then it is at full normal pressure and fills as it should. Why would this be happening and how can I fix this? No issue with the tap on the wall, I disconnected the hose and water runs from the tap fine. Likewise swapped the hose and it's not a blocked hose.