Rep Power: 0

This is my mom's car that she has owned since brand new.
I found used transmissions for $150 with under 100k miles, so anything that costs more than that is out of the question.

Car:
07 Civic EX Coupe
285,000 miles
Trans Fluid Change - Never

Issue:
Turn on car. Shift into Drive. Drives normally for 5 minutes or so. No harsh shifting. Suddenly, check engine light comes on, D starts flashing, car drops out of gear and engine just revs. You can shut off the car, wait about 5 minutes, then start it up and it drives normally again shifting through all the gears smoothly. After about 5 more minutes, it will do it again.

Codes:
P1747 - Electronic Pressure Control Solenoid "A" Short
P1780 - Transmission Control Switch Circuit is Out of Self-Test Range
P0751 - Shift Solenoid "A" Stuck Off
P0752 - Shift Solenoid "A" Stuck On
P0757 - Shift Solenoid "B" Stuck On
P0762 - Shift Solenoid "C" Stuck On
P0767 - Shift Solenoid "D" Stuck On
P0746 - Pressure Control Solenoid "A" Stuck Off

Theory:
I believe it is a Computer Issue as the transmission does not shift harshly or have any other mechanical issues. I believe this is all electrical. I want to check before replacing the transmission just to have the same thing happen again.

 
Rep Power: 125

I'm amazed it's lasted that long.

I'm gonna guess it's gunked to hell in there and clogging up your solenoids.

 
Rep Power: 0

All Parts changed throughout the car's lifespan:
water pump - 16k miles - recall workBrakesBrake fluidTiresOilOil filterAir filterSpark plugsMotor mounts - 2015Battery - 2016
Starter - 2017 - 200k milesShocks - last week
The trans fluid is black. I've checked the solenoids and cleaned them out with brake cleaner along with the filters going to the solenoids. The filters looked clean before cleaning.