When you unload the ender crystals used for the respawning of the ender dragon for example by killing yourself and then loading them again the respawning sequence will continue but the BeamTarget
of the ender crystals won't get updated.
How to reproduce
Kill the ender dragon
Start the respawning sequence
Kill yourself or unload the portal
Come back to the portal
The sequence will continue but the ender crystal beams do not change.
Updating issue with 15w45a info.
edit: Whoops, sorry about that.