Inserting an issue at the lexorank bucket boundary could fail

In the case where balancing has split the issues between two buckets e.g.

0|MIN
0|BBB
1|AAA
1|MAX

If a user tries to insert an issue between 0|BBB and 1|AAA the operation will fail with "Between works only within the same bucket". If balancing is in progress, its possible that the issue can resolve itself. However if balancing is in a half way state and not running, the operation will fail.

Theoretically you should just be able to use genNext() in these cases rather than throwing the exception.