I've been having a similar issue, across multiple different DP cables, (DP -> DP).

My screen will just shut off, and refuse to turn back on for minutes at a time. It will also randomly flicker once every 10-15 minutes (for like 3-4s, then back to normal). I've tried two different DP cables, and two different DP ports, but its the same issue, and the HDMI ports I have don't support 144hz 1440p =\.

Such a frustrating interface. Would love if someone could weigh in with advice.