621 F Case IH wheel loader losing charge pressure to variable piston pump

Hi, We have an issue with losing charge pressure to the variable piston hydraulic pump. We think it something auxiliary, but we can't figure it out, and Case IH is unwilling to provide any tech support. Our dealer is swamped with work, and does not help us either. It makes a popping noise, and we lose hydraulic function and steering, but by moving the bucket, we can temporarily regain function again. It will get bad enough you cannot even steer, and it sounds like the pump is starving. We know the main pump is good.Does anyone have any ideas? This is a new machine with only 3000 hours, it will run for about 20 minutes without acting up usually.