2012 Nissan Pathfinder Power loss

[WayNZ1]

Can anyone help me with my problem. I have a 2012 Pathfinder R51 diesel 450T. Intermittent problem of power loss while driving. Feels like vehicle goes into a protection mode. Will not accelerate or change down to increase speed. Engine revs to 4000rpm with no noticeable increase in speed. When you stop and turn vehicle off it resets itself and is ok until the next random event. No warning lights or faults show on the dash or in the workshop diagnostics. I have had it in to 3 Nissan dealerships in NZ, wth the response " nothing on diagnostics so all is well" Definitely not as this is happening on regular occasions. I have had the SCV replaced with no joy in fixing this issue. Anyones help or advice would be greatly appreciated