Cannot upgrade Lenovo Thunderbolt 3 Dock firmware? Use different cable.

May 28th 2020 — Lenovo, Thinkpad, P73, 40AN, Thunderbolt Dock, firmware

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.