Dell u2711 with right half screen red

[Kaori]

My 2,5 years old u2711 started having this weird problem where the right part of the screen turns red only on black graphics.. if the image is anything else than black it doesn't show red.

I tried to change the cable but doesn't fix it, also the problem seems to go away if I "slap" the top of the monitor lightly, which makes me think there's something not well connected inside..

The warranty is 3 years but I'm afraid I'll get an even worse refurbished monitor, how are they nowadays ?

Also is there something I can do to fix this other than keep slapping the monitor(my current one is new) ? might work for now but it might as well break it for good <_<

Thanks