Got the second DX4000 today and the operation was a success.
So I changed the HDDs from my old NIC-malfunctioned DX4000 to this new one I had ordered without HDDs. Original NAS model is 16TB and the new one is 8TB but this didn’t matter as I expected. Box booted on the very first try. The static IP I had configured didn’t work but saw the DHCP lease and could connect to that IP with RDP. From there I saw the NICs of the new box were now numbers #3 and #4 where the “WDTeam” interface with my original network settings clearly is using NICs #1 and #2 that arent there anymore. Didn’t bother checking how to fix the teaming interface as it’s a lousy fallback setup which doesn’t even work when the controller chip breaks as we have seen.
Then plugged the StarTech USB-ethernet adapter. Installed the drivers for that. Setup a static IP for the interface. Tested RDP with that IP. Tested that the adapter can be removed and re-plugged without loosing the connectivity. So my DX4000 is now back in business.
Thanks for all help on this thread.
NOTE! If you have a DX4000 and you’re reading this, do at least the following: Download and install the driver from https://sgcdn.startech.com/005329/media/sets/ASIX_AX88179/[ASIX88179]%20Windows%20USB%20Network%20Adapter.zip - now when day comes that your NICs fail, you can order that USB-ethernet adapter, plug it in and connect to the DHCP IP gotten