Flowmeter is the most likely issue, something is causing it to hang up, either needs cleaned of the axle shaft in the turbine is broke, remove it and spray with brake clean, then with your mouth blow thru it both ways, it should spin freely and then twitch as it stops, if it doesn’t spin in one direction it likely is the axle broken. You can carefully remove the spiral lock ring and the bearing plate from the flowmeter and remove the turbine to  inspect it .