Hi i just bought an Ibanez Rg 2570 and i have a serious issue, i'm not an expert on guitars so i'd like some help here. After the 14th fret on the first three strings when i play some note (especially on the 17th fret) and let it ring, the note gets cutted out by a strange feedback/noise that's horrible. I can notice that especially if i hammer on instead of picking the note. The problem is that right now the store is giving their luthier the responsability to say if there is a problem or if it's normal for guitars to act like that. If he can't find a problem i'm doomed to stay with that axe, if he finds a problem then the guitar will be sent back and i'll get a new one. Can anyone tell me what can cause this kind of problem? I'm really depressed because that axe costed me a lot (for my finances) and getting it already messed up isn't help me.
By the way, i've noticed that same kind of problem but on a lesser degree even on a strat and on another rg 2570 that they had in the store.

Thank you.