After doing some more research, could it be the turn signal box? I got one off of a junk DSM and swapped it to no avail. But maybe that one is bad too?

Check if the brake pedal lever is no longer pushing the brake light switch in far enough due to a rubber pad on the brake pad lever that deteriorates and falls to pieces over time.

This actually ended up happening today as well but I am having the reverse issue. My lights won't come on at all.
They randomly started working and I have been breaking in my engine and they worked the whole time, so hopefully it's fixed.
I think it's one of those weird DSM things where as long as you're are trying to do something to fix the problem, the problem will go away. But as soon as you stop trying to fix it, it will come back . It just wants some attention is all.

Sorry I gave the wrong link. The brake (stop) light switch goes both (via the green wire) to the brake light and the "turn signal and hazard flasher unit". So you said when you manually put +12V on that green wire the brake lights work?

Normally I would have said the brake light switch is defective or intermittent, but you said you replaced it.

A long shot but I suppose the "turn signal and hazard flasher unit" may have an intermittent short in it affecting the green wire (thus preventing stop lights working). You could try unplugging it to see effect.

Ah! So with that unplugged the brake lights should work regularly? Or not at all?

No, I'm just suggesting unplugging it as a test to see it is causing your problem.

You said you are getting constant +12V on the brake switch's red-black wire? And if you short that wire to the brake switch's green wire (which is what the switch does) the brakes work every time?

That switch is actually 2 switches: brake (pins 1&2) and Cruise (pins 3&4). You don't somehow have the brakes connected to the Cruise part do you?

Oh I gotcha!

I don't think so because they were working for a a little bit.

Honestly they started working again without issue so I'm very confused but can't really test anything until they stop. That being said, I hope I never get the chance to test stuff haha!

Then you probably have an intermittent connection somewhere, in a connector or partially broken wire. Wiggling likely connections, and wires sometimes brings it out. It will most likely return again.

Thank you so much! If it happens again, that's the first thing I'll do!