RVing Drives Me Nuts ---- Electrical Issue

Here's a wiring diagram of the 7-way connector. Since it's affecting stop lights, right turn and tail lights, it's more than one pin (Pins 3&6).

Since you have tail lights on the left side, and not the right side, I wouldn't believe the issue is with your 7-way because the tail lights for both sides are on pin 3.

My suspicion is that your right side bulb is burned out or you have a bad connection between the trailer wiring and the right side light housing. I'd start by putting the left side light on the right side. If it works on the right side, you'll know it was the bulb. If it doesn't work, pull the right side lamp fixture and check for connection issues.

Provided through battery circuit too. Did you try the obvious and clean your trailer connector? Only takes a little corrosion. Normally unplugging/plugging in to the TV will clean off flash corrosion, and if things works again you know some time with a fine wire brush, contact cleaner, and corrosion inhibitor is in your future. I'd start there, then if no joy move onto checking your battery connections and then trace the ground wire to find the frame attachment. If you have a multimeter or test light, you can check for continuity between one of the light sockets to trailer frame, but since it's only one side I'd gamble on being the feed to that side.

Take another plug and using your 7 pin wiring diagram connect a jumper from battery+ to each of the other connections and start checking. That way you will know for sure whethernit is truck or trailer issue.