DIAGNOSIS Intermittent signal loss, often caused by an insufficient quality DisplayPort cable, a marginal connection, or an incompatibility with Adaptive-Sync at certain refresh rates.
FIX Replace your DisplayPort cable. Ensure it is a certified VESA DisplayPort 1.2 or later cable, preferably a short (1-2 meter), well-constructed cable. Cheap or long cables cannot reliably handle the WQHD (2560x1440) signal at 75Hz. Second, disable Adaptive-Sync/FreeSync in the monitor's OSD. Navigate via the joystick to GamePlus > Adaptive-Sync and set it to 'Off'. This stabilizes the signal timing.
IF THAT DIDN'T WORK Update your graphics card drivers. Then, in your GPU control panel, manually set a fixed refresh rate. For NVIDIA: Set to 75Hz. For AMD: Set to 75Hz and ensure the 'Preferred color depth' is not set above 8 bpc for testing. Also, try a different DisplayPort port on both the monitor and your graphics card.
HEADS UP The PA278QV uses a DisplayPort 1.2 interface. If your source is DP 1.3/1.4, some cables can cause handshake issues. Using a 'DP 1.2 certified' cable is more reliable here than a newer, uncertified DP 1.4 cable. Also, ensure the cable is fully clicked into the port on both ends.