oil pressure gauge sticking at 15psi when turned off?

[jt15833]

ive got an electric autometer oil pressure gauge, tee'd off with stock sender. a couple days ago my oil pressure gauge spiked from 50-75 and now has been pretty low so im replacing it, but ive been driving around shifting at 3k because oil pressure is pretty good until there. anyway, just today it kind of jumps around at 25 then when i turn it off will stick at 15, with the car off. it usually goes to resting position when i turn it off, but its not. Im getting ignition and ground signal from the radio harness.