Cannot MIDI map mic parameters in PT9

In Pianoteq Stage 9.0.1, we can now control each microphone's parameters. MIDI mapping the mic enable switch works but attempts to map mic volume or pan fail. The parameters appear in the list and can be assigned to an event. e.g. MIDI CC, but when the configuration is save, the volume and pan mappings disappear. It looks like the parameters are written to the mapping file but not restored.