What type of regulator? If one of the basic inline ones, the way they regulate is via a small orifice (ie., hole) inside the regulator. It's something like 1/16" - 3/32" in dia. After sitting for a while, the pressure equalizes on both sides of the orifice. If that's what you have, you'd better off going to a "real" regulator with a diaphragm in it like the Watts 560 mini regulator or better, the Watts 263A (higher flow rate).
The inline regulators have rather low flow rates of around 1 gpm because of the small orifice. The 263A will give you around 4 - 4.5 gpm. Because water softeners and filters can reduce the flow and pressure, it's better if you start with decent flow and pressure on the inlet side of them.
NOT using a regulator isn't good advice. A regulator should always be used and be installed ahead of filters and water softeners.
I recently installed a Watts 263A regulator inside our TT and have a gauge after the regulator and also a telltale one ahead of it. Have only been able to get 2 camping weekends in so far this year, and both times, the CG supply got up to 80 psi. I've of many cases of CG pressure getting up to the 150 - 200 psi range and that can really damage filters and water softeners.