Scheduled Window Repeating schedule is not always running when it should with Managed Delivery Policies.
Executions are not as often as the repeating schedule is set for.
This is a known issue that was validated in 8.5 RU2.
This issue is fixed in v4 and higher of the cumulative point-fix rollup for 8.5 RU2 found here: INFO5407
Instructions to apply the point-fix are contained in the readme found within the attached archive to the above article.