I have discovered after some confusion that "open door arming" can only be enabled on one door at a time. I kept finding one of the two doors I had set to have "open door arming"  reverted its "open door arming" to disabled so I re-enabled it which was then setting the other door's "open door arming" to off.

It is very confusing to offer the feature at sensor level when in fact it can only apply to one sensor? I see it is also available at system level which makes things clearer insofar as it then displays that only one can be set at a time.

I regularly use two different doors as my entry/exit point depending on whether I am using the car or walking. 

Please allow more than one entry/exit door to have "open door arming". Thanks.