Door Sensor reports open status when it appears to be closed

I have a problem with door sensor(s). The door sensor reports open status when I attempt to arm the system. When I go to the reported door, which is closed, when I open it the sensor flashes blue light indicating that it has opened, despite the fact that it was reporting open status while closed. To make it work properly again I only have to open / close the door a couple of times and all will be well another few days or weeks. I have already had one replaced for this problem and now I have a second sensor failing in the identical manner. I'm beginnig to wonder if this is actually a contact sensor issue or a controller firmware issue.