C4 key doesn't sound on quick soft touch - It's erratic! Sometimes it does.

[aurban]

  Not overly happy after connecting the keyboard controller for the first time. 

One of the keys doesn't play reliably, when playing a legato run or a soft run, a chord or whatever key C4 doesn't play.  Transposing makes no difference.  It's always the same key.

This is very disappointing considering that the music shop isn't exactly around the corner.  What to do?  The keyboard otherwise feels great and appears to be very well built!!  I was so excited, but now I'm the opposite.  Is there an easy fix or do I really have to pack it all up and send it back?

[aurban]

I've tried a factory reset and a flash upgrade.  No changes.  However I learned that it's 2 keys the key 4 semitones higher (E) also doesn't respond well with light quick presses, but C is definitely worse.  The unit has only been freshly unboxed today.

[MajorFubar]

It's faulty. Send it back.
So far you've made three posts about it on two threads.
Not sure what other answer you want.
It's unfortunate, but these things happen on mass produced electronics.