Well it normally does as said run at about 40 at an idle and increases steadily with RPM. When the anomaly happens it stays steady at about 30 and will not move with increased RPM. It happened twice on the way back. Once I shut it off and restarted and it was back to normal, the other time it just popped back while running.

I'm thinking sender may be sticking....never seen it bouncy.....always a steady increase, except when it bounced back to normal that one time.

Never seen a hand held O.P. gauge....is it pressure or electric and connected to the sender?