Hi @bajaMike -
The black Yuanxin adapter is the USB to ethernet adapter. It Is NOT the reason you are having connection issues, replacing it will accomplish nothing.
You may need to replace the Fathom-X, as we communicated to you, but the first thing to check is the tether resistance. If the tether is not connected between the two Fathom-X boards, the link light will not stay on consistently. This board is sensitive to moisture, so if kept in a high humidity environment can suffer from corrosion related issues, even when protected in the FXTI box!
To troubleshoot your problem, share the resistance values you measure:
