So yeah I have a weird problem with my right led tail light, it goes off when I push the brake and slowly lights up again. Brake light does not work either. I already cleaned the circuit board and used electrical spray.

I was wondering if it was a ground problem, so are there separate grounds for all of the tail lights?

 

Did you test the power going to the light and compared it with the other sides? You may just have a bad tail lamp, see if you are able to mount the right tail light to the left side.