Tranny isn't easy to diagnose, though It doesn't sound like the TCU usually that involves electrical malfunctions and CEL comes on.
Sounds more like something mechanical going on inside the trans is starting/gone to crap, if I had to begin to guess. First start by checking the basics like thre fluid and its condition. Then check and see if the TCU has any codes. I would also check the ECU while your at it.
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