I haven't experienced anything like this. I know there's a TSB on the 7AT from 2013 (13-001A) - it includes reprogramming the transmission control module, but centers around a specific error code (P0710).
2013 z service bulletin 13-001a
My '13 7AT had an unrelated ECU error code last fall, and I had the dealer apply this TSB while I was there. I haven't experienced any issues with manual mode as you describe, though. Your '14 might have this transmission update installed from the factory, though; probably worth a dealer visit.