Shift Solenoid E Malfunction - '01 V6 AT

Hi all. About a month ago, my truck started shifting really hard. I got the CEL and had it read. Code P0770 for "Shift Solenoid E Malfunction" was thrown. I had the code cleared to see if it came back, and it did. I took it to the dealership and had them run their Toyota diagnosis on it, and they also said it was "Shift Solenoid E Malfunction." I told them I wanted to order the part, so I got it and took it to my transmission guy. He replaced the solenoid and I went to pick my truck up. It drove great and shifted as smooth as ever for about 20 miles before slowly beginning to shift somewhat hard, eventually shifting hard again. Now, the truck shifts smoothly after startup but after 5-10 miles each time, it begins to shift hard again. I'm not entirely sure if it has anything to do with it warming up because sometimes it will still shift smoothly after getting up to normal temperatures.

I took my truck back to my trans guy, but I'm curious to ask if anyone here has ever run into this same problem. It seems to be rare or unheard of based on transmission shops I've spoken with.

Thanks in advance.