Check inside your winking light for the earth.
I had similar on my 4/4. I did the “wiggle test” by wiggling the wires under the wing. It recreated the effect.
Took the lens cover off and saw the earth (black) wire was a bit loose. It was pop riveted to the light body and not a tight connection.
Drilled it out, cleaned everything, bolted it back with a stainless bolt. Worked well after that.
