DIAGNOSIS G-Sync/Adaptive-Sync handshake failure. The monitor and GPU lose sync, causing a temporary blank.
FIX Disable Adaptive-Sync in the monitor's OSD menu. Go to Game > Adaptive-Sync and set it to Off. Test. If the blackouts stop, the issue is the sync protocol. Update your NVIDIA or AMD GPU driver to the latest. Re-enable Adaptive-Sync. If it returns, leave it off or try a different high-quality DisplayPort cable.
IF THAT DIDN'T WORK Check the monitor's refresh rate setting. In Windows, right-click desktop > Display settings > Advanced display. Ensure the refresh rate is set to 240Hz, not a custom or lower rate. Mismatched rates can cause blanks.
HEADS UP This is almost always a software or cable issue, not a failing panel. Use the DisplayPort cable that came with the monitor.