I did not come across your post until now. I had a similar problem last year. I played with the pressure regulator and then bypassed it. I used a 10$ in line regulator.
I reconnected the original and back flushed it and then it worked fine. You might try that? Option #2 is my first action which helped a lot, both in terms of the problem an me personally----I gave it a whack with a rubber hammer! It helped but did not totaly solve my problem
I recomend that if you try that use a RUBBER hammer and just tap it a few times, before actually whacking it. I believe I had some grit or calcium built up in the regulator. It did turn out to be one of the lesser problems with my plumbing.
The other thing to look for is a kinked water line between the pressure regulator and the backflow valve (assuming one was installed) where the intake merges into the trailer house lines.
If I were having more of a problem with calcified lines I would think about flushing with dilute muatic acid, but that has its own little addtional details to deal with.
You have my sympathy, it is a pain
. I had enough other problems with plumbing I am replacing my lines, heater adding an acumulator and some creative valving for multi methods of draining or bypassing or isolating lines and fixtures.