Be sure you are in the correct forum for your vehicle.
Give the model year....Engine size...transmission type (auto or standard)
vin number can be very helpful.
Did you buy the vehicle new, if not, how many miles were on it when purchased? How many miles on it now?
Describe the problem the best you can.
Tell us what has been tried, if anything.
If the vehicle has been to a repair facility it would be nice if you can scan or take picture of the bill and attach it to the post.
This information can save a lot of time and get you the answers you need much faster.
Both share common GO6 ground point (above RR wheel house behind panel)... interior ground points not typically been concern..
Quick down and dirty be to remove bulbs from the sockets, and look in each socket,,,, there you will spy a small stip of metal that "ideally" supposed to firmly ride the side of the bulb base for ground supply to bulb.. is it indeed laying flat or slight below surface of socket ??
Take and hook the bottom of that "finger" and bow it out into the socket' bore so the bulb base contact it firmly,, and try your lights again.. do this to both the turn signal socket,, and the stop / tail socket.... ALSO,, make sure bulb for tail-stop is properly indexed into socket.... see them 2 pin on bulb base,, match them to proper deep / high slot in socket so we have low watt filamet with tail light on,, and high watt filament with stop light on