Diagnosis
This is a signal interruption, commonly caused by a failing cable, a marginal connection, or an adaptive sync handshake issue.
How to Fix It
Replace your current DisplayPort or HDMI cable with a certified high-speed cable. For 144Hz at 2560x1440, you need a DisplayPort 1.2+ or HDMI 2.0+ certified cable. Ensure it is firmly connected. In the monitor's OSD, navigate to 'Display' > 'Adaptive Sync'. Temporarily set it to 'Off'. Test if the blackouts cease.
If That Didn't Work
The issue may be related to the monitor's power-saving features. In the OSD, go to 'System' > 'Power Savings' and set it to 'Off'. Also, disable any 'Auto-Scan' or 'Input Auto-Switch' features in the 'Input Select' menu to prevent the monitor from searching for other signals.
Heads Up
If using a GPU with NVIDIA G-SYNC Compatible mode, ensure you are using a DisplayPort connection, have the latest driver, and set the monitor's refresh rate to a fixed 144Hz in Windows before enabling G-SYNC in the NVIDIA Control Panel. An unstable overclock on the GPU can also cause these dropouts.