When exporting a project from Clarity PPM to Microsoft Project (MSP), Task Start dates are changing to the Actual Thru date of the assignee for tasks that don't have any time posted against them and even though constraints are set on the task. The task start date will change to the first working day after the actual thru date for the resource on the project if the Actual thru date falls on a weekend. This does not happen for tasks that have actuals posted.
This is caused by DE44318
This issue applies to the MSP New Driver
This issue is fixed in Clarity PPM 15.6. This issue is also patched in 15.4.1 patch 4 and also 15.5.1 patch 1 (and higher).