Terminal frozen displaying 1057

My 4K PVR is frozen with "1057" on the display.  It doesn't respond to the remote or the power button.  When I unplug it and plug it in again it says "boot" for a few seconds and then shows "1057".  Does anyone know the significance of that number?  Browsing the web page I found some error codes but no mention of that number.

When the display changes from "boot" to "1057" the TV turns on, but says that the source isn't turned on.  So, apparently something happens on the HDMI cable, but it doesn't have a valid signal.