NVIDIA GTX 1080's & DELL U2414H's DisplayPort issue

It is about NVIDIA GTX 1080 (MSI Gaming X) and DELL U2414H (not) working together properly. I have already read about some issues with that model on the web, but it seem to be too late.

I had three DELL U2414H monitors, all connected via miniDisplayPorts to NVIDIA GTX 1080 (MSI Gaming X). There was also a projector connected via HDMI as the 4th screen.

The rightmost DP was always working bad: it had some probability of working. When it did not work, the solution was to unplug it and replug in a minute. It worked with 90% probability! There was visible difference between working and not working screen in nvidia-settings:

  • 2 lanes shown for working monitor, and only 1 lane (with the same 2.7 Gbps throughput) for not working;
  • broken resolution for not working monitor - usually 640x480
  • it was not recognized as a DELL monitor, but as ‘NVIDIA something…’
    That third DP had been stopping working when I turned the monitor off/on and sometimes on system reboots. I’d been doing that ‘unplugging for a minute solution’ for a few months after each power off. That solution was something about DELL saving settings which needed to be reset by unplugging for a minute… I don’t understand what a chaos is it. That thing was really annoying but I rarely turned off my machine so I did not report it.

Months passed, and now I have another, more dangerous issue. Everything I connect to the rightmost DP stops working in a few days.
Firstly, the miniDP socket in the monitor stopped working at all. In nvidia-settings the was the only visible difference: 4 lanes instead of 2, with the same throughput of 2.7 Gbps.
Than I bought DP cable (not mini) and replaced the mini one with it. It ended up in a few days with the same conseqences. No matter what I connect to that monitor socket it does not work anymore! I do not believe it is the monitor issue. I think it is about video card burning them out someway.

My subjective conclusion:
The rightmost DP socket on my video card is deadly because it:

  1. Sends wrong signal (the first issue with 1 lane and broken resolution).
  2. Burns monitor sockets (the second issue with 4 lanes and broken miniDP and DP sockets on my monitor).

It is very weird issue so I do not want to return the GPU because no one will be able to reproduce it.
Does anybody have any thoughts?