Rear tail light issue

Hey everybody!

My rear driver side tail light used to just be dim. And randomly only some times my left turn signal would stop working when I’d press the brake.

Now it seems to not be dim anymore. My new issue is that the same light (driver side tail light) doesn’t stay on as a running light, instead, my turn signal light stays on. And when I turn my left turn signal on my turn signal and brake light flash but not even at the same time!

Would this be a ground issue? If so, where would I find the ground? Or something different at play?
I don’t know much when it comes to electrical so any and all help is appreciated!!
Diagram and pictures are my best friend hahaha

Thanks in advance!!!
PFA

 

I would start with cleaning all the sockets with a fitting brush in a drill .

I use CRC 556 in the socket to remove corrosion and help keep it from returning.

Do the front as well ,\.

New bulbs or clean the metal parts as best you can.

Then see what your dealing with.

All the bulbs ground through the sockets.