Quick tip, as it took me two hours to resolve. If you are trying to update your Thunderbolt 3 dock from Lenovo (in my case Workstation Dock Gen 2) and you are stuck on "Wait 20 seconds" loop, try to switch Thunderbolt cable to one you received in box with your dock.
I'm using DeLock 1.5M TB3 cable (20gbit) fine with this dock, but firmware update was stuck as visible on screenshot. Swapping temporary to one included in the box (60cm, 40gbit) fixed that, firmware updated successfully.
Many KVM switches (local and IP) from major companies like Dell, HP or IBM are manufactured by Avocent. Those KVMs use special cables known as SIPs or RIPs to communicate with managed machines.
In normal scenario only OEM and Avocent cables work on particular device, but as I discovered - at least in one case this was simple to bypass and allow any existing SIP to work.
This article summarizes my journey and discoveries while hacking Dell 1082DS IP KVM.