Displayport - Losing connection on Asus X34P

[Glazarus]

I've got a setup were my PC is a few meters away from my screen in order to have a clean work area. 

 

The problem I've encountered is that my displayport cable's length seem to be affected by interference. The included cable seem to work fine, but the longer randomly lose connection, blanking the screen out and then directly returning with a "DP" logo in the upper right corner. Sometimes the screen totally lose connection. Interferences can even be done with a candle lighter, clicking on the flame close to the screen (!). The cable I'm using is a 5m DP-4050 Deltaco cable that is shielded, which makes me wonder why it so easily get interferences. 

 

I've been looking at active cables, but I'm not sure if they work as intended? If interferences go through a shielded cable, is it really the length that's the problem or this specific cable? 

 

Is there a 5m Displayport cable out there that's shielded, active and has little to no risk of interferences? No one seems to know.