P2419H and Latitude 3571 - random signal loss

I have a Dell laptop 3571 and a Dell monitor P2419H. I am using Ubuntu 22.04 with newest drivers. Tested with Windows too, same behavior.

When I connect that monitor, it works fine but will randomly have signal loss meaning just a black screen fow a few seconds. But the OS doesn't detect the monitor as missing. Sometimes every few seconds, sometimes after a few minutes. Sometimes instead of just a black screen there is a warning saying, that the resolution is not supported. So it seems there is a problem how the laptop communicates with the monitor, because the resolution is set correctly. I also tried different cable and different ports. My other monitor works just fine with the same cable and setup! I also have another dell laptop 7530 and it works with the exact same setup and cables for hours with no problem. I also tried updating drivers. no chance. (Intel drivers for Ubuntu seem to be automatically installed and I haven't found a way to change them ...)

I also tried to turn of integrated GPU in BIOS, but it seems that this is not possible. The other laptop only has an NVIDIA card and works with no Problem. Maybe the HDMI Port is not providing enough power to the USB Port? But it Works just fine with other Monitors even at 4K over a 5m long cable.

Also the first time I used this monitor it was a different one at work. Alsready there i noticed, that the Monitor was sometimes loosing signal but it was only a few times and then it worked for hours without problems. So it seems this is not a Problem with only this monitor, but with ALL of the line. So probably something with the laptop.
(The laptop has a bend in the middle, but except the webcam is broken, everything else so far was working. Maybe its a hardware fault ? ...) But then i don't understand why all Ports should be effected.