The default voice limit in HALion Sonic SE is rather low. You can increase it by opening the HALion window and setting it in the options. In the forthcoming update we’ve bumped this to a higher value.
Some samples (in Garritan, for example) are processed in a way that makes repeated notes sound tenuto and sound like one sustained note. Not sure if this is the situation you are encountering, but it might improve as Expression Maps are implemented.
Thank you. Increasing the voice limit fixed that and the score is playing, admittedly using a lot of memory, but with very low CPU, even with a lot of ambience.