I recently had a customer having this issue with his trans where sometimes it will shift to neutral between a 2 gear downshift and this causes a very long defuel where the truck falls on its face before finally getting to the right gear. It does this both from going from 5-3 and from 6-4. The tune in the truck is stock minus the DPF is deleted out of it and the egr is turned off. I took a screen of the log to show exactly what its doing. It does this probably half the time.