gkellum, and other staff at Eventide,
it seems like I have solved the problem. If that’s the case, then the problem was in my end – my MIDI controller (Boss ES-8) sent out MIDI CC message #080 by default on all MIDI channels in conjunction with every MIDI PC message. It was in a submenu on the Boss ES-8 that I hadn’t even discovered. After I turned off the MIDI CC messages, the H9s seem to work great and respond swiftly, without freezing etc. So my fault!