Help! My portable keyboard has a serious issue!

[jdog127]

So, the E and F keys (on EVERY octave) will not play if one or the other is being held down. For example, if I played the keys C-D-E-F-G, what would result is C-D-E-"nothing"-G. But if I play them separated without holding the E key down, everything sounds as it should. I pried open my piano (that took way to long) to try and see if anything was obviously wrong. Nothing that I saw seemed to be wrong, and the fact that it's on every octave makes me ponder what could possibly be wrong with it.

I have a Yamaha DGX-200.

Also, I have emailed Yamaha support about it. I'm trying multiple venues in the interest of time.

[hfmadopter]

The best I can offer is that it seems unlikely that this issue would be mechanical.