Hello
Try changing the ActionEffectCode to 1. Since you are specifying the percussive sample in the line
<CustomOrganRank> ...
<IsPercussive>Y</IsPercussive>
you shouldn't need to specify the action effect as percussive also, this is considered a normal action, just that the percussion notes are single shot.
Note that when treated as percussive, loops (silent or not) will be ignored and the note will play until the sample end. If you need to use silent loops for a certain special feature then you need to treat the sample as sustaining and it will also require a release marker (cue marker).