I am runnig the latest GPO update. I am on a MAC with DP as a sequencer.
Actually I first noticed this problem even before the last update: the lower two A flats on the cello have a muted or muffled sound, noticably much less resonant than all other notes. This is true both in the legato mode and with alternating bows. The upper A flat seems fine.
Which cello are you referring to? There are 3 solo cellos plus 3 derived player instruments for each of these. Changes in timbre (sometimes drastic ones) from note to note are common in acoustic instruments and this is often reflected in the finished programming. My suggestion would be to try the other cello choices if something about a particular instrument does not fit your particular application.