I know this post is oldish but I'll share my 2 cents anyway.
Mine was working fine for a long time and then I brought it into work for a little VR party. Then the grey flashing screen started once I set it back up at home. Take a little while for it to start but then progressively gets worse. I thought maybe it's because I've start playing a sit down game (Elite Dangerous) where as I used to only be playing room scale games. So I tried pointing the sensors a bit more towards me because they are both a bit behind me. Didn't help.
I was playing without a headphones one time and I notice the grey flashing got really bad when I heard the fridge kick it cooling up a notch (or maybe it was the aircon, can't remember). So maybe it has something to do with power interference. I'm going to trying running the power cables away from any other cable so they're not overlapping and have them in their own powerpoint so they're not sharing power with any other appliances. Hopefully that shows some improvements.
