Okay, I just had chance to try it again with mixed results. The good news is that the door physically opens so it just seems to be the alerts and status that are out of whack.
First attempt, I got open/closed/open/closed alerts back to back. The door opened and the status reported as "closed". I then used the app to close the door and this worked fine but no alert received.
Second attempt, I got open/closed/open alerts. The door opened and the status reported as "open". The door subsequently closed okay and generated the closed alert.
On my setup, the position of the reflector relative to the door position means that I get an open alert once the door has moved up around 12" and the closed alert when it is a similar distance from being completely closed, so a back to back open/closed sequence is very unusual and would only occur if the physical operation was interrupted. I can confirm that this hasn't been the case.