Lenovo ThinkPad USB 3.0 ProDock

[AlbanRampon]

2. This is not what I suggested. Isolating the issue to see where the issue lies needs to only vary 1 parameter at a time.
If we change everything at the same time and it works, it doesn't tell us what was wrong. If we vary one parameter at a time, it will tell us something.

3. We don't get any monitor plugged in event. It could be that the hotplug detection circuitry in that dock is defective. I think at this stage the best would be to contact the manufacturer and ask for a replacement. You can indicate that DisplayLink told you the monitor is not seen by the dock. To speed things up, you can give them a link to this post.
Just one last thing to try would be to change the cable between your monitor and dock, as this is the only thing I believe we haven't checked.