Codes P0740 and p078a, transmission?

The problems I've had with this car have been countless, but until recently every problem I've had has been okay enough to at least still drive the car with (air leak that nobody can seem to find for example). That is until today. I had been having the code p0740 which is a code pointing towards the torque converter. My car had gotten to where it did not want to shift up after around 4th gear. So, I did the two cheapest possible fixes first (changed the transmission fluid and filter and replaced the torque converter clutch solenoid.) After doing so the car seemed to drive much better for the first day, until we drove 75 miles the next day. Once almost back home the car revved high but didn't want to move. We parked the car and used the code reader we had handy, and it showed p0740 again as well as p078a. Once turning the car off and restarting it, it drove for about 2 minutes before doing the same thing again. I was able to get it home since I was in my road thankfully when it happened. I'm hoping it was maybe a defective solenoid I purchased but worry that may not be the case. Any advice or tips would be very appreciated. Thanks!