Turn signals don’t work when headlights are on

Sometimes you have to "improve" the grounding. If nothing else, clean and solder a pigtail ground right to the socket shell.

You can troubleshoot and "prove" the problem by getting the problem to "show". While the problem is thus happening, stab a test lamp or meter directly onto the side of the socket shell. Stab the other probe into ground, be sure to get through paint, etc. If the socket is ungrounding you wil l read a voltage.

If that shows nothing, carefully probe the actual lamp shell thorugh the slots.

OR IF NOT JUST WIGGLE THE SNOT OUT OF THE BULB LOL