Most likely you haven't done anything wrong. Maybe made things too pretty.
The 69 outside lamps get ground through the bumper. Sometimes that isn't making a connection.
Get a piece of wire. Touch one end to the light bulb base when it's installed. Touch the other side to a good sheet metal ground or to the battery (-) post. You probably need to use the battery post 'cause you have a shiney car.
Turn on the signals and see if this changes how it behaves. The idea here is to put ground right to the light bulb if that makes sense.
Guessing it's one or both front marker lamps not grounding to the bumper or the bumper isn't grounding to the frame.
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