Jira Corrupted Index
If you see any symptoms that your Jira index is corrupted (for example, your JQL queries return wrong data), disable BigPicture, perform Jira reindex, and enable BigPicture back.
Work breakdown structure data is stored in the BigPicture table called:
T_DEP_STATE_VERSION
T_DEP_TREE_EVENT
T_DEP_LINK_EVENT
T_DEP_NODE_SIBLING
If you have a backup that contains such a table, your WBS can be restored.
Maintaining a Jira index is critical - when the index is corrupted, synchronizing tasks can result in data loss (the existing task hierarchy is changed). When the index is corrupted, JQL does not work, and the plugins treat all the issues as new upon the synchronization. This means that the task structure based on artificial tasks changes during a sync. The old structure is lost.
More about Jira index corruption can be found in the Atlassian documentation:
Impact on synchronization
Full synchronization is not run when BigPicture gets information about the corrupted index from the Jira API. A user can perform a Jira reindex. This should solve the corrupted index problem. Users can also continue without reindexing, which can cause irreversible and unintended changes in Box scope.