There is a script that runs to sync Clarity and JIRA. After the script is run, the WBS sort numbers are updated and some are duplicated.
Symptoms seen -
Release : 16.0.2
DE66972
Fixed in 16.1.1
Patched 16.1.0.1, 16.0.3.2
Workaround -
Export the project to OWB and save back without changes