We added a workflow validator that ensures that a certain custom field is given a value whenever an issue is created. However we had already created a number of issues prior to adding the validator, and some of those issues did not have a value in that field. When we try to clone one of those issues the workflow validator prevents the clone from being created (which is to be expected). However no error is reported on the screen and the cloner link is created from the original issue back to itself. Also, if the issue had sub-tasks then we end up with a sub-task link from the parent to itself which we cannot remove !