MAN TGA with tipping saddle problem with the air

Hello guys! I absolutely need help! It’s a TGA saddle with hydrodrive and leaf air suspension and D20 engine with a cylinder compressor. Now my problem when it’s loaded wants to compensate the air suspension and then he has to advance again a bit and put on hand brake again that makes him maybe 3 times then he doesn’t get away because the air is gone. He has to run the truck under the loading bridge always with 1800 rpm otherwise he gets worse with the next because it has to wait until it is fully pumped. Can one of you help me there doesn’t know what that can be about. With the other trucks you have that’s not so! No error entry available. According to test protocol air system, by MAN, everything is fine. Can this also be due to the trailer? Thanks already for your efforts