Brake lights don't work when headlights are on. Turn signals both work OK. on 2001 Chevrolet Express 3500

Brake lights are OK when headlights are off. Turn signals work OK. When the headlights are on, the brake lights don't work. Also, shift indicator flashes with the turn signals, then goes off when the brake is pressed.

Poor ground at rear lights. May need new socket panels or wire repair.
You bet! Good luck with it.