In preparation for the "Island Sanctuary" added in Patch 6.2, the number of instances created had been increased significantly. However, this limit is being reached on certain Worlds, particularly Balmung and Cerberus, where we are seeing significant instance numbers compared to other Worlds on the same data center.
We are currently looking into supplemental measures such as the inclusion of backup server machines. In the meantime, should you receive a message indicating that the server is busy when attempting to move to a different area, we ask that you wait a while before attempting again.
Thank you for your understanding and we sincerely apologise for the inconvenience.