I've been noticing some strange behavior with the Mirror Universe NPC groups. Apparently many of the npcs in the groups have messed up spawn animations. Instead of using the beam in animation, they're using the beam out animation which causes them to look like they're beaming out and then pop back in. Some are missing beam in animations entirely.
I put together a test mission to demonstrate. Mission start is at the console outside the transporter room on ESD. I haven't done anything to the groups other than set them to visible. Just activate one of the consoles to spawn the corresponding group.
Misson Name: Mirror Beam In Bug Test
Mission ID: ST-HJMSRGMEY