I'm going with you may have a bad ground to the lights
the reason some of this may work (even dimly) is one wire is seeking any kinda ground thru it's neighbor wire.
I see this happen a lot with the lights on trailers
i had to screenshot the upper and lower halves of this diagram as "prodemand" would not let me copy it
looks like black is the ground (the right side of either diagram is the brake/ tail lights)
as a test, you might run a temporary jumper wire from ground, to the black wire to provide it with a "for sure" ground, till you can find the "open" on the original circuit. It may even look grounded, loosen the anchor and scooch it around or clean the area.
You should be able to see where diagram one overlaps diagram two
the medic
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Saturday, November 21st, 2020 AT 5:14 PM
(Merged)