Thanks. Yes it builds to 50 and shuts off with the faucet closed or even half closed so that makes sense. Now I just need to decide if it's worth messing with it. If I leave it as is I need to re prime after the power has been off for a few days. Not the end of the world. When it's connected to power it will fill itself back up every few days.
If you have a pressure tank that fills to 50 before the pump shuts off, it might hold enough pressure on the foot valve to keep it from leaking back.