PO is not involved enough into Sprint execution, i.e. no approve for "Done" product increment (if UAT process it requires) or UAT process has changed
Discovered by combination of metrics:
Time in Status, when equivalent of "Product Owner Review" increases
Productivity: Committed vs Completed, when decreases
Productivity: Average velocity by sprints, when decreases
Scope: Backlog Health, when low or ok, but with the above issues
Recommendations:
Introduce or enhance UAT process
Introduce or enhance change management process
Introduce or enhance stakeholders management