I now see rapid the input lights blink rapidly once I introduce the HDMI cable
I had seen the same behavior with the VGA adapter, that took too much current from the miniHDMI and lowered the 5v on the RT2x board to 4v, at least that’s what what I’ve measured.
Strangely as in your case, everything was fine for a few days.
First the led blinked for a fraction of a second at power on when the RT2x was new, then for a second, then forever…
My RT2x died with the same permanent blinking lights.
I can assume that the device connected to the miniHDMI port takes too much current and somehow affect the RT2x negatively.
Perhaps removing the 5v from the miniHDMI port will be a good solution for future revisions?