In your scenario and keeping the same song without change,

Is this a multi-style RD ?

Have you changed the RD? Do you get the same infill behaviour?

On the RealDrum Settings dialog there is a [_] Developer Mode.
The manual pg422 reports that usually this is for user creating RD styles
but it records errors and it seems to record some info that could be helpful in diagnosing this behaviour.

RrR