The bulb is a 3157 iirc, and they are prone to overheating & deforming the socket.
The contact area between the bulb and socket is very small, and can easily corrode to provide intermittent connection.
I had tried everything checking connections checking everything I finally decided to try a new bulb!
So far so good. Thanks everyone for responding I'm 66 years old owned alot of cars never had a bulb work intermittently