I have a six line manifold and a three line manifold in the kegerator - separate regulators. Back in the day I thought I might need to run different pressures sometimes.
Friday two lines off the sixer quit letting CO2 flow. One keg went to a drizzle so I started checking. Yesterday one line started working again for no apparent reason. The other was still semi dead this morning although it was pressurizing a tiny bit when I pushed the QD pin. I don't get it. All have backflow valves as I remember.