Have 98 peterbilt 379 that the right turn signal is sending power back to left side.?

If brakes are press while right turn is on all lights light up like brakes. Left turn on and brakes press everything works fine.|||I do know that these lights do some strange things if each light is not well grounded. Check the grounds first between the light and the frame , otherwise the electricity tends to go back up the ground of the other bulb and throughits lead wire to eventually find ground.