Tranny slipping - P0894 after rebuild and new refurbish

[laborde2122]

I blew a tranny line on the highway about 4 months ago in my 2006 Chevy Silverado 5.3l. It had 170,000 miles and is clean and has run real well up until this point.  I decided to have it rebuilt with a 3 year warranty because even after I get a new daily driver, it’s a good work truck.
 

After I got it back, it would drive fine then shift rough after I came down from highway speeds. When I turn off the truck and restart it, it shifts fine. After I get back up to higher speeds and come down, it acts up and shifts rough again.  Eventually it threw the P0894 code. I took it back and he said it was a sensor or something. Next day, hard shifting and code again. He said it must be something else with the tranny and fixed fixed that (CV something maybe?)  (Sorry I don’t remember both of these repairs, but I can find out). Couple days later, same code and rough shifting. He replaced the tranny this time with a manufacturers refurbished. Next day, same code and same rough shifting after highway speeds, but in addition to this, a message appeared saying Transmission Hot. 
 

Thoughts? Haha. I’m lost and I think my transmission guy is as well at this point. I don’t want to keep socking him with it if it’s something bigger than the tranny going wrong, like electrical stuff. If it is something with the transmission and he should be the one fixing it, I want it on him. I paid good money for that warranty.