Shuddering from fridge freezer and dripping tap?

My recently-installed fridge freezer works fine but occasionally (usually at night) it starts to shudder. It also does this sometimes when i use the water dispenser. The resolution is to push on the end of the kitchen cold tap (which drips when the fridge shudders)

Is this an issue of water pressure,or an air bubble somewhere, or something else?
How should i fix it?
Many thanks

Simon
August 2009