why does celtic wind accordeon behave like this?

[RJBMusic]

Within Cubase C4, I use the right hand accordeon patch from Bela D Celtic Wind. It is loaded in Kontakt 2.
My problem is that sometimes in the midst of a sequenced phrase a chord is only played like a very short staccato while I programmed a chord of a couple of beats.
This happens randomly it seems. Although when it starts it continues to do so until I load the song again.
Does anybody know the cause of this behaviour?

I found out that an organ patch also loaded in kontakt behaves the same, so it must be Kontakt or Cubase

Cheers,
Ruud Jan