10 speed down shifting right before it should be upshifting!!!!

Anyone else have this issue or hear anything like it? Car is a ZL1 with over 700rwhp. Car was fine for a few weeks after leaving our shop with a fbo package. Runs great but all of a sudden the car started to downshift at wot. And I mean fully engaged in a pull cars flying and then right before the car is ready to upshift it DOWNSHIFTS and the rpms hit the rev limiter and scares the ever living shit out of you. It has done it in both manual mode and off a straight punch. I've scanned it and everything else seems fine. Oh and the trans has not been touched or tuned.

Any ideas?

Yikes, no one had anything like this happen. Any theory on why?