mobile

I purchased my first Droid 4, the seller said it was in excellent condition, so i can say esthetically is great, but I quickly found a problem in the physical keyboard: when I press certain keys, these return their letters + another one. I tried an app to remap those keys, but does not work...when I press the keys in the remap app it seems to get the input of two keys at the same time ... this makes me think that it may be a hardware problem. I hope you answer me that it is possible to solve via software...
There's a video of the problem, to give a better idea https://www.youtube.com/watch?v=5G_PjHXgTRo

Thank you!