I have managed to get it free ( had to tear apart the ceiling tile it was mounted on ) and get the dome removed.  There appears to be a rubber gasket on both the microphone and corresponding area of the dome that I think over the last couple years "stuck" together.  They are both deformed after removal with the camera side gasket pressing deeply into the dome side. ... View more

That's the problem though, the security screw was installed, so I cannot unmount it without damaging it, or the ceiling it's attached to. ... View more

It's an MV12, and yes I've checked the installation manual.  The dome won't twist to come off. ... View more