Very Weird Transmission Issue

[nickelplease]

So I have a 2011 370z nismo, only mainly driven on weekends, spirited driving here and there. But over the weekend I was doing a couple pulls with my buddy in sport mode and it locked me out of 5th and 6th gear and popped up yellow triangle for s-mode and wasn't showing any gear indicators on the dash, so I turned it off and turned it back on, everything went back to normal, now here's the weird part, it will go 1st-4th gear smooth no problem, then when going to 5th or 6th it will go in smooth and show on dash it's in either of those gears but will act like its in neutral and not actually engage the gear. But if your at a dead stop and try 5th or 6th gear it will engage it and pull the drivetain. I'm 81 miles over my warranty and the dealership isn't liking that so looking for any help.