At the moment this is hypothetical, but could easily be a real situation.
Leave home without arming system, with a rear door(contact) open.
Rear door is listed as must be closed in order to arm away
At some point, realizing the system is not armed, I attempt to arm the system via a dashboard, but get a HSM message "System not armed, back door open"
Any way to get around this and arm the system?
At this juncture arming the system with the back door open is in my opinion better than leaving the system disarmed. The back door sensor will not cause an alarm unless it is closed then reopened, and if armed anyone walking in through the open door will be picked up by any motion sensors.