MP gauge needle "jumping"

[drauk]

What might be causing the needle on my MP gauge to jump after seemingly sticking? In particular, when decreasing throttle setting I've noticed it stick at a particular point for perhaps 1 second and then jump down about 2 or 3" worth of MP. It doesn't appear to be carb-ice related in that application of carb heat doesn't seem to make any difference, plus it happens in circumstances not conducive to carb ice.

[Windy Militant]

Drauk,
Could be many things but usually two main contenders.
1) Mechanical I'm presuming that the gauge will be a Bourdon type. So the gauge could actually be sticking due to wear, lack of lubrication or dirt.

2) A slug of moisture in the line. This has more inertia than the air that should be there so either causes lag or if positioned in a certain place will cause an air lock until it moves then allows a rush of air through.

Either way I'd suggest you get it looked at before you blow the engine due to faulty reading.