Transmission puzzle

Hello all new to this site. My problem is with a 2003 chevy trailblazer, transmission related I think. Take the vehicle out the transmission shifts no problem 15 minutes into the drive the transmission is not shifting through the gears from a dead stop, it feels like it is taking off in 4 gear. This is an automatic that was rebuilt buy a reliable transmission shop Code P0785 is coming up on the scanner 3-2 shift solenoid circuit. All help will be appreciated Thanks

how did you already need the tranny rebuilt? hopefully it is still under warranty