I am guessing this probably is not the problem, and I don't want to make things sound silly or simple, but when I lock my Pontiac with the key fob or the internal delay system, my back up lights stay on for 60 seconds. Same thing if I unlock with the fob. It is programmable, and I have it programmed that way for my own personal needs. You may have a similar delay.
On my LF31 RV, I have a similar delay, but it isn't programmable, as far as I know, and it is the parking/running lights that stay on a short period of time.
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