This issue is targeted to be fixed in Clarity PPM 15.6.1.Workarounds:
Set milestones to Task Mode
of Auto Scheduled in MSP.
For already impacted milestones: Change the task to auto scheduled in MSP, then update the start/finish dates to the correct date.
To change the Task Mode for a task:
- Option 1: Go to a task view in MSP, and select Auto Scheduled from the drop down. Any Tasks that are Manually Scheduled will have a thumb tack in the Task Mode field.
- Option 2: Double click on the task in MSP and change Schedule Mode from Manually Scheduled to Auto Scheduled and click OK
Revert back to an older Microsoft Project Update. Link to one MSP2016 update where it does not happen is the June 6.2017 update from Microsoft: KB3191934
Note: It's recommended to test the impact in non production to make sure reverting back doesn't introduce any issues fixed on later updates.