Welcome to the forum.
Are the lights you refer to 12 volt or 120 volt?
Is it all electric going off or just the lights?
Suggest the first thing is to check the battery(s) condition/charge, then inspect/clean all the connections on the posts, being careful to not mix up the wires.
Once you make sure the battery(s) are ok and the posts/cables clean and free of corrosion, see if the lights work better.
The converter is there to use the incoming 120volt power and charge the batteries--all the 12volt items work off the batteries, not the converter.
If the same thing happens if not hooked up to 120volt (shore power) I believe it is bad connections and weak batteries.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired