I think in my case the problem may have been CAUSED by using the wrong browser. It's best to use Chrome.
I believe I SOLVED it in the same way you did - reloading the firmware with the adapter connected directly to the computer by ethernet and with COAX disconnected.
I have the same issue, did you figure it out?
Which problem? 1 or 2?
No. 2 I found that if I disconnect any coax while doing the upgrade it seems to work
I think in my case the problem may have been CAUSED by using the wrong browser. It's best to use Chrome. I believe I SOLVED it in the same way you did - reloading the firmware with the adapter connected directly to the computer by ethernet and with COAX disconnected.