Also, some other thoughts:
3rd wire from top - the insulation wasn't stripped off enough and there is some of the plastic jacket under the screw. Maybe same thing on a a few other connections but hard to tell from angle of photo.
As a general routine thing, check tightness of all connections at the 12 volt panel. Also, is there enough of the wire under each screw - should extend past each terminal a bit. While you're in there, check connections in the 120 volt section too.
99% of electrical issues are caused by bad grounds! Check frame ground and battery ground connections as they sometimes can be loose and/or corroded. Check battery connections and positive connection at battery going to the converter. If there is a mini circuit breaker in the A-frame, see if the pos battery wire runs through it and if connections are loose or corroded.
Use a voltmeter and see what the voltage does when "pulsating". Does it dip down a lot or a little? Disconnect battery and check voltage for state of charge and also see if the converter voltage is correct. Unlikely the cause, but is the 120 volt line voltage good? Do all lights pulsate or just the ones on one of the circuits? Do they pulsate the entire time the furnace is running? Do the lights also pulsate when extending/retracting the slides?
Is the wiring factory or done by an owner? Curious why 600 volt rated building wire was used. If not original, perhaps there's a bad connection somewhere beyond the panel due to non-factory work? Where is the negative wire for each 12 volt circuit connected - is there another bus bar somewhere? If so, maybe there's a bad connection there? I would have expected the negative connections to be at the bus bar on the right. Actually, the more I look at the pics, it doesn't seem factory original.
Not sure what brand that converter panel is, but maybe it's simply old and tired and needs replacing.
We had some flickering lights and I traced it to an improperly crimped connection at the switch - courtesy poor factory workmanship.
