Oystein, what exactly are you using for your cable extensions?
My successful extensions use commercially-made shielded USB cables. Only a few inches are the unshielded Blue Robotics twisted pair.
In the post you commented on recently, I just cut up a regular desktop USB 2.0 cable. More recently, I’ve been cutting up high-flex cables from LCom that have polyurethane jackets: http://search.l-com.com/search/Category-USB--keywords-high_flex
In your video it looks like you have some black-wrapped cables inside the electronics enclosure and a yellow sub-sea cable outside? It also looks to me like the yellow sub-sea cable doesn’t just carry USB signals?
Are any of those true purpose-built USB cables?
In a properly designed, high-quality cable suitable for streaming high-rate data over a long distance, the green/white D+/D- pair isn’t just a twisted pair, it’s a 90 ohm controlled impedance twisted pair arranged with respect to the ground, power cables, and shield so that the D+/D- each have a specific impedance to the shield. The insulation on the twisted pairs is a particular thickness and material to achieve the right impedance, and this is hard to achieve in a hand-built cable or a shielded cable that wasn’t designed specifically for high-speed USB. Higher data rates and longer cable lengths require more precise cable design.
If the D+/D- lines run next to other data lines, the signals could potentially be corrupted. They should only share the inside of a shield with power and ground lines, if anything, and those power and ground lines should have extremely clean power signals running on them.
What works over 10cm (short twisted pair cable supplied by Blue Robotics) won’t necessarily work over a meter or more, even with shielding and careful twisting. And keep in mind that even the highest-quality USB 2.0 cables with precision design are only specified to work up to 5m length.
Lots of commercial USB cables don’t follow all of the cable specification rules either, and sometimes it works but sometimes it doesn’t.