Neautral wire overheating

It's unlikely hat the EMS is causing the problem. Properly done screw connections offer no more resistance than any other point in the system. I would go back and double check everything you did before the problem started. My guess is that the extra length of extension cords is causing the problem, or that possibly the additional cord is made with the wrong size wire. All 30A cable has to be 10g a, even the neutral. A shore power cord over 100' should be a size larger.
You are going to have to start eliminating components until you find what is causing it. Remove the EMS, you are going to have to anyway to repair or replace it. Reconnect the wires and use a clamp on meter to measure currents. Turn off all of the AC breakers and begin turning them on one at a time and see if you have an appliance or device that is drawing excessive current. Do the same thing with and without the new extension cord. it sounds like a complicated process, but it's simply eliminating one potential problem at a time. You may need to enlist the help of an electrical savvy person to do this.

Somewhere you are going to find a neutral wire that is undersized or a high resistance connectionand causing to much current to be drawn.

You buss work appears to be extruded aluminum. You need to be using a good de-oxidation compound. Colloid copper may not be enough. Read label closely before applying to aluminum busss work.
The connectors for the cable entering your surge protector do not prevent the intrusion of moisture. You or manufactuer should seal to prevent moisture if used outdoors.

IN and OUT are the two highest amperage loaded points in the circuit. I go to the hardware store and purchase appropriate size tubular wire brushes to fit the holes. Disconnect from shore power and inverter, remove one wire at a time and ream the hole with the wire brush until it gleams. Scrape the wire strands bright shiny clean with a utility knife. Brush on the colloidal copper and tighten the set screw. You need not do this to the two holes with the long screws that attach the buss to the fixture.

Next, do the POSITIVE feed wire in and out connections. You'll have to "Do Them All" In and out wires. Then go do the buss and feeds in your fuse and breaker panel. Do this once and do it right. But you do need to re-check to make sure something weird is not causing the set screws to loosen. I "trust" nothing.

TIN plating is only moderately effective in stopping corrosion and electrolysis. Copper can be used in a DIRECT aluminum to copper termination or junction. Gold, is invincible except with aqua rigea (don't give me a hard time with this SPELL CHECKER!) but we know how that goes, sigh.

All Hardware stores of note sell colloidal copper "assembly" compounds in various sizes from blit tubes to tubs.

It's nice to do something once, do it correctly, then do plop in a lounger by the pool crack open a brewskie and say "ahhhh"

I guess i can try these 2:colloidal copper compound and reaming the bus bar. The screws are snug and the wires appear clean. My surge protector is shot from these 3 meltdowns. Thank God for the lifetime warranty! Hopefully progressive don't try to weasel out of it. I've had that experience with warranties before.

KcBorne wrote:
Would that mean the surge protector is causing resistance? Because it is heating on both the IN and OUT lines right at the terminals. No where else.

If that is the case your terminal connections are high resistance. Follow Mex's advice

Would that mean the surge protector is causing resistance? Because it is heating on both the IN and OUT lines right at the terminals. No where else.

Diddy-Bop on down the list of threads until you find

ELECTRICAL WIRE FIRE

It's not that far down, you'll find it fast.

Read all the responses

The set screws in the buss bar must NOT be loose as a goose in their threads.

You MUST ream out the aluminum bus bar to get brand new shiny aluminum

The wire strands MUST be brand new shiny copper penny color

You MUST use colloidal copper compound

And re-check a week later. If he screws keep getting loose REPLACE the buss bar.

The set screws must tighten down against a little friction.

Resistance equals heat. So if it is getting that hot you have dangerous issue you need to deal with NOW before you have a fire.