Since the upgrade to Atlassian Plugins 4 (CWD-4121), the plugin upgrade manager has failed to run:
org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'pluginUpgradeManager': Requested bean is currently in creation: Is there an unresolvable circular reference?
The regular UpgradeManagerImpl continues to run successfully, but this is an issue for plugins which include upgrade tasks.