You made a very good point, I was also doubtful regarding the connectors. We have only four channels, Vdd, GND, Data+ , Data-. There is no shielding. It is true that USB standard cable has two more shields, but I think that for the 2.0 that we use we don't need it. I found that these additional shields (purple-orange, blue-yellow)are for USB 3.0. Not sure why this was chosen. There is no shielding on the pcb. The connector of the camera has a 5th channel but we dont use it. Do you think this might be the cause?
I don't have physical layout available right now, but I could show some part in a photo. I hope they provide it to me soon so that I calculate this impedance. I measured the ohmic resistance, would that help? The problem is on the long cable for the one of the cameras. The following values are for a good working pcb. Normally I loose the streaming on the camera with the long cable.
For the long cable, the ohmic resistance is:
when pcb off: Data + channel: R =0.2 Ohms, Vdd channel: R = 0.2 Ohms
when pcb on and not streaming camera: Data + channel: R =0.3 Ohms, Vdd channel: R = 3 Ohms
when pcb on and streaming camera: Data + channel: R = 0.8 Ohms, Vdd channel: R = 87.6 Ohms
For the short cable: the ohmic resistance is :
when pcb off: Data + channel: R =0.0 Ohms, Vdd: R = 0.1 Ohms
when pcb on and not streaming camera: Data + channel : R = 0.0 Ohms, Vdd: R = 1.2 Ohms
when pcb on and streaming camera: Data + channel:R = 0.1 Ohms, Vdd: R = 36.8 Ohms