X15 stopping without engine brake on

Hey guys, I've got a 2022 International HX520 with a X15 in it that does something very weird. Sometimes when I lift my foot of the throttle the turbo starts to whistle and slows down the truck without the jake brake being on. The jake brake has 3 levels with the first utilities 3 cylinders, second engages all 6 and the 3rd level is the added braking power of the variable geometry turbo. For some reason the 3rd level engages without the other 2 even though the jake is set to 0/off. This happens every time I stop the engine and start it again and it usually stops shortly after I get on the freeway.

Added bonus to the situation is that since it has a ultrashift, once the turbo kicks in it drops a gear or 2 and completely stopps me in my tracks especially when empty.

I've been to 4 different shops (3 International and 1 Cummins) and no one has ever heard of anything like that. One shop foreman even tried to convince me, that this is perfectly normal without being able to explain how is that normal. I've spoke with Cummins customer service and they've said they've never heard of that. The same answer I got from Eaton saying they only supply the transmission, but they're not responsible the gear dropping as the engine is the one that controls it in this situation.

On a separate note, the transmission itself doesn't work very good as it does not differentiate between being bobtail on a level ground and a tail wind and pulling black mountain at 130k gross. It always changes gears at the same time with the same sequence. No matter how gentle I'll push the pedal it will not change gear before 1600rpm and it will always skip the same gears regardless of the weight or terrain. Eaton said it needs calibration, but even after it got calibrated, it still does the same thing. Any thoughts on this?

Has anyone of you guys experienced or heard of such bizarre behavior be it in x15 or other engine/transmission?

 

Yes, when the truck enters into regen it really spools the turbo and pushes the rpm up, but it doesn't slow down the truck or at least doesn't do it noticeably. What I'm talking about is a situation in which the engine is actively trying to stop the truck from moving using the turbo as a jake brake while the jake brake is not active. When this happens you can either accelerate or slow down, there’s no middle ground.