Don't assume its your relay or surge protector - it could be your shore power reel. Do you have a powered shore power cord reel? Using a meter- check the voltage at your pedestal receptacle, inside your transfer switch box where your shore power cord leads (3 wires plus ground) come in. I had a bad Glenndiming Power Cord reel that was not making contact inside the reel. They say to never adjust your shore power cord length under load.
Glenndiming did a quick turnaround on rebuilding it in 10 days & it was only $75 plus freight both ways. While it was out of the coach, I bolted all the leads together with #10 bolts & taped each of them with electrical tape, so I could continue to run off shore power.