PO Product Owner is not involved enough into Sprint execution, i.e. no approve for "Done" product increment (if UAT User Acceptance Testing process it requires) or UAT process User Acceptance Testing process has changed
Discovered by combination of metrics:
Time in Status, when equivalent of "Product Owner Review" status increases
Velocity: Committed vs. Completed, when team does not meet commitments leaving sprint backlog in not completed state by the end of iteration due to the fact that Definition of Done which includes PO acceptance on sprint basis cannot be achieved
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