Electrical System Going Haywire

So, I am having one of the most bizarre issues I've ever seen.

After doing a simple electrical repair on my tail lights everything worked PERFECTLY fine for about two days, then out of nowhere things went crazy. It started with my signal lights flashing once then staying on, then when I turned off my headlights I lost power to the engine and it almost stalled until I flipped the headlights on again. When I got home I started playing around with lighting configurations and when I would turn the right signal on it would flash my entire dash on and off and the license plate lights would alternate (I would also hear the shift interlock making noise). When I turned the right signal on only the front turn signal illuminated. When I turned the hazards on, it would flash the dash lights and only the left license plate light.

It gets even weirder...

I started the car and drove it around, I noticed when I pressed the brake with the headlights in the "off" position the dash lights would illuminate and when I let off the brake they would turn off. This is already so insanely bizarre to me, but when I turned on the headlights, my transmission would go into first gear or neutral (depending on my speed). The same thing would happen when using either signal or my hazards; my transmission would switch to first or neutral.

Here is some footage of the problem:
https://www.youtube.com/shorts/EhiWCHUeSP0

I am at a complete loss and didn't even know this was possible. I am under the impression there is some grounding issue that is affecting this whole situation. I tried checking the fuses corresponding to my lights and all of them were fine, both in the cab and under the hood.



A little backstory:

My brake lights and passenger tail light have been out for a few months, I knew that the reason they were out was because of the faulty connector on the driver-side tail light (Connector R6). I finally got around to buying the ridiculously expensive OEM connector to make the fix.

When I started the repair, I noticed the new connector had six wires, while the one in the truck had nine (some wires were doubled up). I assumed this was just another example of poor electrical work from the previous owner, as his repairs have caused me issues before. Since the doubled-up wires were connected at the connector clip, I assumed that they could simply be spliced to the same wire that corresponds to their position. (Does that make sense?)

This is the old connecter with nine wires:


Is this factory wiring (9 wires)? Or is this a result of aftermarket wiring work or a trailer harness situation?

This is me splicing the new OEM connector to the old one, I spliced one at a time being mindful of the position on the clip (the red/black wires are just an extension to the wires on the OEM clip because they weren't long enough):



What doesn't make sense to me is that my fix worked completely fine for two days of driving and I drove around 100 miles. I'm curious if this is not even a problem associated with this situation, although due to the timing, it only makes sense.

Has anyone ever experienced something like this? What confuses me the most is the effect it has on the transmission. I'm sure it's a safety mechanism but there's obviously something very wrong and it's affecting multiple electrical functions of the vehicle. I can't imagine changing a taillight connecter would have this widespread effect on the entire vehicle.

I'm planning on replacing wire by wire but if someone has any idea of what this could be it would be much appreciated.

 

I’m sorry, it’s all I’ve got.

 

anything helps I guess

 

Not sure if auto trans function is tied to the brake sensor, if so I’d check that switch and wire.

 

Sounds like poor grounds to me

https://charm.li/Toyota/2004/Tacoma...Diagrams/Electrical Diagrams/Ground Circuits/