HDMI stops working when USB keyboard is unplugged

Strange phenomenon: HDMI works (except for a short black screen very 20 seconds or so), but the signal drops when I unplug the USB keyboard. The X15 stays operational (as I have an open SSH session from my desktop), but there's no more image on the screen. Any clue? Thx.

I purchased a new BBX15 last week from Mouser and have a HDMI issue wherein I don't see any display from the monitor connected to the HDMI port. But the user LEDs are flashing on power up. Any idea whats the issue?