Driver side blinker (turn signal) is faster when brake pedal applied 2001 4WD DXL Automatic

Searched to death with little luck. any assistance greatly appreciated.

Truck details
2001 Tacoma 3.4L 4WD DXL Extended cab 200k miles
No lift kit, no alarm
Aftermarket components: Radio
When did you first notice the problem?: A week ago
How often does it occur?: Every time
Have you checked codes?: P1135 (O2 sensor)

Truck problems
Initial problem was TAIL 10A fuse under the hood would blow, resulting in no dash illumination when headlight switch ON, no rear DRLs/license plate lights.
It would blow seemingly at random while driving, possibly triggered when driving over very bumpy roads.
But, all other lights would work after fuse failure, including brakes.
That has stopped happening, and I do not know why.

Issue now is the driver's side turn signal blinks 2x faster ONLY when brakes are applied. IE when I'm at a red light and turning left.

• Pulled tail light covers off, inspected bulbs while a friend went through turn signals/braking/parking lights etc, all bulbs are fine.

• Swapped all rear passenger-side bulbs and drivers-side bulbs; the problem persists on driver's side.

• Swapped the entire tail-light assemblies next (so they are on backwards, in a way), and the problem persists on the driver's side.
• Removed factory tow/hitch wire assembly, problem persists
• Replaced brake bulbs, problem persists

While left signal ON and brakes ON, car in (P)ark, rear driver's side lights do the following:

1. the two filaments in the brake wires go on/off at different intervals (one is on other is off, then they swap, back and forth, quickly)
2. back-up/parking light is very very slightly illuminated
3. turn signal blinks faster

Although the 10A TAIL fuse looks good visually, I changed it just now to make sure it's not the fuse, and problem persists.

I do not have a multimeter but can buy one. I have the FSM in .pdfs and dug through the wiring section with no success.

Sorry for the long story y'all

 

Does your truck have a trailer harness? If so, that is probably the issue.

 

Not anymore, I've removed it.

Today I took the tail light assemblies off, then disconnected the battery. Then reconnected the tail lights, then the battery.
For some reason, that has solved the problem for the time being, although I would not be surprised if the issue comes back.