About a week ago I installed Conbraco Series-36 pressure regulator.
City water pressure is 90+psi. Static pressure right after the regulator
is 50psi (default setting). Whenever water is used City pressure stays
about the same but pressure after the regulator (pressure gauge is
about 5” away from the regulator) drops down to 40psi or even 30psi
(depend on water usage). This is totally unexpected behavior. At the
far end (next to open faucet) pressure may drop significantly (even
down to 0psi) but right after the regulator it should be close to the
whatever it set to (50psi). Am I right? All my plumbing pipes are 1/2”
and closest faucet is about 15-20 feet away.
Something is wrong with this picture but what?
What should I check and how to correct/fix this problem?
Is my regulator simply broken and must be replaced?

Thank you,

- Vitaliy