I also suspect moisture. If the new regulator is doing the same thing as the original, I would remove the regulator and disconnect some of the lines and blow them out with air. Do not blow them towards any appliance. Blow them backwards toward the regulator open line.
If you find moisture in the lines I would install a T fitting where the flexible line meets the hard line going to the RV and put in a short drop pipe with a cap as a trap. I would also change your propane supplier if you have been using the same propane source.
I have been in temperatures below 20 degrees without any freezing problems. Good luck; Frank