Displays dropped out mid game, no longer detected
During a gameplay session, my Index displays went black (but still powered) with no warning. After restarting SteamVR, the displays refused to power on at all and I get the "Display Disconnected" 208 Error, while the power and USB functions appear to be intact (as much as can be tested with no displays). I have tried all combinations of restarting the PC, changing display ports on my GFX card, reinstalling drivers, using different version drivers, resetting SteamVR USBs, reinstalling SteamVR, disabling direct mode, buying a new tether cable, and testing all of the above on a second PC, to no avail. I have also gone thru the steps provided by Steam support and their diagnosis was that the headset was faulty, not the cable. My Index primarily gets used for seated simulators, so I don't believe this is the result of physical damage/wear, leading me to suspect an internal component failure.
I am capable of ordering and following the iFixit guides to replace components, but is there any way to diagnose where in the chain of I/O Board > I/O Board Cable > Motherboard > Displays that this failure is actually happening?