U4323QE, screen blackout during switch on or hibernate on

Hi There,

My friend uses two Dell 43" inch - U4323QE monitors. Both are connected to the DP ports directly on his desktop system. His desktop (Dell OptiPlex 7000 Tower) is capable of handling 3 DP inputs.

The issue I came across is, one of these 43" inch monitor (U4323QE) is displaying black screen with no output at very random times. This started two weeks ago and no changes were brought in for this to happen. I have tried below;

• Changed to a new DP cable provided by Dell to the affected monitor
• Changed the DP port from the current connected port to an available port (out of 3) 
• Swapped the DP ports with the working monitor

None of these seem to have worked out and in-fact this gives me an idea that the GPU seems working. This is happening at random times when I switch on the computer or when I try to resume from hibernation. Any suggestion would be highly appreciated.

Thank you in advance.