Brian,
If it is going into limp mode (stuck in a specific gear), there really should be codes that are related.
If you presently have the car at home, try to retrieve codes yourself and let me know what you find. Because of the model year, this vehicle has an OBD1 system that doesn't require a scanner to retrieve codes. All that you need is a very basic voltmeter or multimeter that can check continuity.
Take a look through this link that explains in detail how it's done. Let me know if you are comfortable doing this.
https://www.2carpros.com/articles/mitsubishi-trouble-code-definitions-and-retrieval-procedure-for-odb1-system
Also, I attached a copy of the wiring schematic for the transmission. I highlighted the wires that are related to the transaxle solenoid valves. Note where they all go to. Each one is controlled by the transaxle control module located under the dash in the vehicle.
The chances of two solenoids failing this quickly are low. I suspect there is either a wiring issue between the solenoids and the control module that is being temporarily fixed when work is done. After a short time, the connection is lost.
Of course, that is a theory at this point. However, before I would replace more parts, I would wiggle wires, disconnect and reconnect harnesses and inspect them, and see if it makes things work again for a period of time.
I
Let me know. If that has been done, then it's time to start checking wiring for faults. If one exists, it is likely in the transmission. The solenoid valves are attached to the valve body. See pic 3 below.
Let me know if you are able to get codes or if there is anything I can do to help. Also, let me know if the valve body was replaced during the overhaul.
Take care,
Joe
See pics below: Note: I had to cut the wiring schematic in half to make it readable. However, I did overlap the two pics and highlight the wiring involved.
Images (Click to make bigger)
Sunday, December 26th, 2021 AT 8:12 PM