Brake light messages

[johnflight1]

2006 ML350 I keep getting brake lamp left and brake lamp right and substitute bulbs on. I have replaced the lamps twice even though they ohm out good.
I have cleaned the removable sockets contacts and they work for a little while after that and then go out again shortly after that .
The bulbs always check good but the messages are correct the lights are not on! the substitute bulbs are confirmed on. Could this be a problem with the lighting electronic box that is back there behind the right wheel well???