Inspection of the UnixCluster.php assign() function shows that a transaction will be left open if a UnixClusterAccount object already exists for a CO Person record.

This is specifically causing an issue for OrgIdentitySource syncing when there is a Pipeline attached to the OrgIdentitySource and the Pipeline is configured to establish cluster accounts.

Note that while enabling a Pipeline to establish cluster accounts is new functionality intended to go into the 4.5.0 release, having unbalanced/opened transactions is bug no matter how assign() is called.