[100IH]

The needle bouncing steadily leans toward tight lash. Erratic bounce, sticking guide, weak or broken spring. Sloppy stem clearance and washed out cam lobe might be a steady but low reading. Compression test-wet&dry, vacuum test readings, cylinder leakage test and lastly this vacuum gauge sans check valve if needed is about as much help as a fella can get. Good luck. One thing we do know, valves won't stick closed over night. They can bounce, leak, wobble and dance or stay open. Then there are rings but that ought to be consistently low, not intermittant. Sorta like herding cats.