I had a leak on my cold water line under the bathroom sink, but not until our 3rd outing. I tried tightening the screw fitting above with my hand, but it wasn't loose. Didn't leak any more after that, on that trip, or the other 2 we took later. I figure the tightening pressure must have been enough to seal it.
Perhaps you can feel whether it's getting wet above or below the pex line.
2019 Wolf Pup 16FQ - bought new 3/2020
2013 F150 5.0 STX SCab 4x4 SB/3.55 rear/tow pkg./36 gal. tank/1695 Payload/7350 GVWR