An intermittent problem like that - where the device works perfectly for an indefinite time, then randomly becomes malfunctional junk for an indefinite time - is usually caused by overheating. Can you reproduce this problem then measure temps on your monitor and on it's power supply brick? I suspect your G-Sync module (under the enlarged area on the back panel) is the cause, especially if you're running at >120Hz - Asus had to overclock this 120Hz-rated part and mod it with a phat heatsink, but in hindsight that didn't always work out too well for them. Try to assure that the monitor has unrestricted airflow around all sides, don't stuff it into a tight little monitor-sized box/shelf, move it a few inches away from the wall, move the power brick a little distance away?
Another possibility might be an intermittent/defective DisplayPort signal - perhaps the cable is damaged or one of the end connectors is loose? Perhaps you sometimes kick it, pinch/bend it between your desk and your wall, etc, while gaming? I assume you're just using the plain DP-to-DP cable which came with the Swift, but if you're using any other DP cables, adapters, converters, or extenders you can have weird problems - there's tons of underspec (and uncertified) DP cables on the market.
And are you sure it's not GPU failure? A good way to check would be to swap monitor while the Swift has this weird display issue ... if the problem isn't isolated to one monitor then the monitor isn't the cause.
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