Tasks on your project are changing unexpectedly (on their own) from 'Completed' to 'Not Started' (Closed to Opened) when exporting from Clarity. Another symptom noticed may be that the task % Complete is changing from 100% to 0% when using MSP.
This issue is due to settings in MSP not being set to the recommended setting in working with Clarity. For a full list of required and recommended settings, see: Configure default settings in MSP to use with Clarity
Release : All Supported Releases
Component : CLARITY MICROSOFT PROJECT (MSP)
If the above doesn't help, see the following KB: Task Status of Completed changes incorrectly back to Not Started