Issue with notes not playing sometimes.

Currently, I'm working on a part with the English Horn.  Sometimes notes do not play. The velocities are around 60.  I've tried tweaking the note start or end points to get control of this but have not been successful. I've tried different programs (Legato close wide, Legato close, etc.) but am not getting predictable performance. I'm have to constantly mess with the notes. Is this just part of a new plugin's vagaries? This is frustrating.