thereishope

That's annoying! Surely it couldn't of gone off coincidently when the time delay finished? Could you wave for longer then open the door to be sure? The timers are globally set (not by sensor) so it doesn't make sense to me unless something is broken on the door sensor like PeterJames mentioned.

Yep that is the test or purpose - arm as if you were at the panel and see if it also has the issue. There should be a delay set to arm to allow you to exit. It may also be set to 0 (default 45 sec, range between 0 - 255secs)?

To prove that theory could you arm using the smart phone app while standing at the panel (wait to hear it is going into arm mode)?

Do you think it may be only doing a partial arm? Do you have more than 1 zone/partition setup? Perhaps when you arm through the panel it is only doing a partial arm and the smartphone app doesn't have that flexibility and arms everything? Have you tried on the remote? Check settings on arming or you could bypass that sensor and check you still get the message?