Pressure regulators do go bad eventually. We are on our third one in 15 years. They are the brass ones, not the cheap plastic ones.
We use a short piece of hose, like the ones that come with some of the filters, at the spigot, then the reg attached directly to the filter, then whatever hose is necessary to the rig. Instead of a 90* fitting at the trailer, we use a faucet with its own shut off. Gives the advantage of the 90* fitting with the option of drawing water outside.
We also use quick disconnects on all hoses. Much quicker.
2010 Zinger ZT19RD
2000 Dodge Ram 2500 Cummins 4X4