Strange mixer tap

I fitted a new mixer tap in the kitchen three months ago. The cold tap works fine with no problems, but the hot tap is very strange. Turn the hot tap on, water flows for a second, there is then a judder and flow goes to a trickle. Open the tap further and it flows as normal. When you come to turn it off it sometimes takes only one or two turns when you know you have opened the tap at least 3 or 4 turns. Sometimes it flows normally for 10 seconds or so, and then it reduces itself to a trickle. I know the boiler is not at fault as we had the boiler inspected and serviced by the manufacturers mechanic, and he reported no faults. So I'm convinced it's the tap. Any ssuggestions for a cure? Thanks, Peter