Upon starting the Crystal Tower - Labyrinth of the Ancients the first barrier goes does (after everyone is out of loading screens etc.). As always, the raid moves straight forward and at the intersection everyone is supposed to go left towards the poison pools & bone dragon. However, occaisionally (Friday 4th of April & Tuesday 8th of April - the only 2 days I've tried) the barrier does not go down at that intersection, making the raid unable to progress at all, and forcing everyone out to sign up again and hope the issue doesn't come up this time.
I've heard people associate this with a wave of 90k errors that were happening (on Phoenix) right before we tried getting in on Friday evening.
Overall it wouldn't be that bad of an issue, but since CT has become a bit less sought after waiting times have increased quite a bit. And having this happen after a good half hour to 45 min of waiting is quite annoying.