"Powdery" Chocolate

Still struggling with the texture of our chocolate. It's better since we started using the micrometer to make sure the max particle size is sub-25 microns, but still "powdery" (not actually gritty, but definitely not smooth like it should be). Seeking the wisdom of the crowd and those who have gone before. We're doing our conching/refining in a Santha 11, if that helps. We're running some tests on (improvised) conching after refining, improving out tempering, adding cocoa butter (some of our chocolate is a lot more viscous than others). Any thoughts for which rocks to turn over first??

Cheers,

David