The flashes are made up of 'noise' or 'snow' if that makes sense. Sometimes it's like the whole screen for a second (especially when the game is loading something or processing graphics more). Sometimes it's random pixels and horizontal lines. I also noticed in Oculus app that my HMD is no longer registering as connected to a USB 3.0 slot, even though it is. NONE of my USB 3.0 slots work for the HMD, but they DO work with the sensors. Is this the same as what you are experiencing?
Do not waste your time with a windows reinstall I have already done this and it makes no difference still random static white flashes.