Sensor armed away and then flips to armed stay

Hi ... I've been experiencing an issue when my employees lock up for the evening. They arm the system on the panel for "Armed Away" and then lock the front door and leave. Exactly one minute after they arm it and go, I can see in my email notifications that the system has changed to "Armed Stay" and then another notification that "the front door has been bypassed." I then go through my app and re-arm to "Away." This doesn't happen every day, and I've asked my employees if they are doing anything differently that day when it happens, but they say they are not.

Can you please give me some insight as to why this could be happening and how to prevent it? It's frustrating and I don't want to risk my business being unarmed in times when I'm not checking my email or app right at 5pm. Thank you.