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.
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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.