Bad city connection check valve cause low water pressure?

It's probably a defective check valve. The valve may have come out of the the mount, missing retainer clip. That's why it appeared crooked,out of place. With the pressure from the city water, it's pushing the valve piece too far and obstructing water flow. It probably doesn't stop the water from leaking out when using the pressure pump either.
Relativity cheap and easy to replace..

Ken