Disklavier

I bought a used DGT2A, and am very happy with it, but I recently noticed something a little peculiar, and wonder if someone could confirm that it's normal for this model (and possibly others).

Between Bb and B one octave above middle C, there is a noticeable change in two respects. Played loudly, the attack on notes above this point is slightly softer. More noticeable is that, when played softly, notes above this point decay very quickly after about one second, instead of tapering off normally.

I suspect that the sampling was just not as robust on the higher notes, but I'd feel better knowing for sure that it's not an issue with my particular instrument.