Lazy converter?

Just got back from a recent trip and while I was plugged in at the camp spot, the converter was acting odd.

I have a voltage gauge inside which lets me know how the house batteries are doing while dry camping. When I'm plugged into AC that gauge will read 14.3 volts and eventually (depending on battery charge) will idle down to 13.7 volts and remain as long as I'm plugged in. But this time I would notice that on occasion when I started using more electrical devices (lights, fans, etc...), the gauge would start reading 13.3 and lower like I was no longer plugged in. Clearly NOT doing its normal thing. In fear that the batteries would be drained, I reached down and reset the converter breaker and it would jump back up to 14.3. I tightened up all the electrical connections just to be sure nothing was loose and possibly the reason.

I went through watching the voltage gauge fairly closely for a couple times over two days and then decided to see what would happen if I just left it alone. Knowing that it was doing the same thing, I could tell the lights were dimmer for a short while and then everything would brighten up as it seemed the converter was running normal.

Is this something I should be concerned with? Is it just normal converter actions? Could it potentially be related to the batteries in any way? Is there something I should be looking for?

Also, this is a WFCO 55 amp converter. Thanks for the help or advice.