The Back to Previous post-function is currently based on OSWorkflows Histories.
It means that to allow to go back to previous Status, it check Step Histories provided by OSWorkflow Component.
A side effect : When you change the Workflow for the related Issue Type, the Workflow Entry is changed, and then OSWorkflow returns only the Step History for this current Workflow Entry, and not previous Steps.
With this improvement, if no Previous Step (different from current Step Id), then we use the Status history (Issue Change History) to find the Previous Status, then related Step Id in the current Workflow.
If the found Status is not in the current Workflow, the Back To Previous does nothing; and Warning message is traced in JIRA Logs.