When did this start? Start with the easy item. Verify that some "friend" did not place a small jumper wire across the AUX and marker light pins on the 7 pin connector.
This video uses a flasher, but will give you an idea of which pins to look at.
I bet your problem is at the end of your 7pin cord. The wire nuts are probably loose, and a couple wires are touching each other.
Track down the tail end of the cord, it maybe 7-10 feet long. At the end there maybe a junction box or not. Maybe inside or outside the TT. Check the wire connections.
Outside running lights stay on
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