Task duration changes in Fixed Duration tasks in MSP

Symptoms:
Upon selecting “Update actual hours” option in linking, even if there are no actual hours to update, the duration changes on some Fixed Duration tasks. Since they are completed tasks it inflates the work hours and the actual hours, which causes discrepancies with what Changepoint shows.

Reason:
Possible reasons for the task duration changes are listed below. One or many of these conditions may be observed in the impacted project.

1- There are advanced constraints (such as "Must start on date...") which may cause MSP to auto calculate work/start/finish/duration

2- In MSP under Project Calculation Options, the option “Updating task status updates resource status” was not checked.

3- There are time bookings prior to the Planned Start Date of the task. In such cases, unfortunately MSP ignores the update of actual time, if the task is a fixed duration task.

Resolution:
Resolving 1:
Remove advanced task constraints

Resolving 2:
- Link project to MSP with “No update” option
- Go to Tools –>Options ->Calculation tab
- Select the option “Updating task status updates resource status”
- Click OK and save project. There may be conflict resolution messages at this point; such conflicts need to be resolved by the PM.
- Close the project to upload the plan to Changepoint

Resolving 3:
-One alternative is to extend the duration for the assignments in MSP so that it covers Start/Finish, save back, and then link to MSP again with update detailed time option.
-Another alternative would be to change such tasks (i.e. having actuals prior to planned start) to a Fixed Work task.