I had the same problem of the base flashing red after the firmware update. Here is what I've found, not all USB cables are the same. Some provide data while some only charge. I tried the firmware updates with a different USB cable and viola! All good. I would recommend running both firmware updates with a USB cable that is not just a charging cable.
Good luck, rock on!
Same exact issue. Updated both TX and RX and have flashing red on RX. Left unplugged all night, same issue still. RX base flashes red, TX solid green. Unit does not work after FW update, worked fine before. Not happy.