I find that a 'top-tip' for this is to wrap a stretchy Velcro tie around the gooseneck - this adds no weight and acts as a drip stop for when working at acute angles.
try changing the angle of the brush head,
Dave, are you using an aqua dapter? One of mine had a leak and I had the same problem.
wrong angle so the water is running back down
Is there a leak from the Y piece or the hose from the Y piece to the jets