pb278q 1440p monitor not being detected properly

My 1440p 60HZ Asus pb278q monitor is being defaulted to 640x480, but my other 1080p one is fine. I replugged it (displayport) and it displayed the correct resolution but made kde vanish and crashed the system 5 minutes later.
The "Identify" button correctly identified the name after the replug.

Please help.
GTX 980
Asus z97 deluxe