2015 F150 5.0 6R80 6th gear shift

I?m running a 2.9 Whipple and after getting my last tune modification I am experiencing a miss shift going into 6th gear. Drive the truck normal and let if shift into all 6 gears (reaches 6th at 42mph) let off the accelerator to 40mph and step back on the throttle lightly and the trans goes to a neutral. Let off throttle and it catches back into 5th gear. Aggressively press the throttle and it will go into 6th and drive all day long there. When I drive from a stand still to 75-80 and use 3/4 throttle I have zero shift problems. When I put the truck in sport mode I get the same results as above but at 62 mph.

My tuning guy just got back from Sema so he is a little busy....does anyone know off the bat what could fix this?

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Originally Posted by St0nieismyd0g

does anyone know off the bat what could fix this?

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Yep, the tune before this one, lol. Without seeing a log and tune who knows?