Turn Signal Gremlins

[vanderbilt]

I've got a 1970 C10 with some electrical gremlins in the turn signal/brake light area. Both the front and rear LEFT turn signals work fine when the brake pedal is NOT depressed, but stop flashing as soon as I hit the brake pedal.

In addition, the rear RIGHT light flashes when the LEFT turn signal is on. However, the opposite is not true - only the RIGHT rear light flashes when the RIGHT turn signal is on. A prior owner spliced in a trailer pigtail which might explain some of the issues, but I can't wrap my head around why both rears flash only when the LEFT signal is selected.

Perhaps a related issue is that the hazards work only when the turn signal is on (either side). If you depress the hazards button, nothing works until you put on the turn signal. Is this normal?

I apologize if the issue is fairly obvious - I'm new to troubleshooting electrical issues and my site searches didn't come up with any shenanigans too similar to mine. I have the wiring diagram for the truck, but am so new to electrical issues that I'm not sure where to start. Any advice is appreciated!