I'm sure this has been discussed/posted here before, but I couldn't find anything on it. I have a PM who has a project of 430+ tasks including summary tasks of which 54 detail tasks have resource assignments. The balance of the tasks are what are being called tracking tasks for schedule. When the PM does his updates in MSP v2010 and uploads to Clarity the dates on the non-assigned tasks are being skewed and then skewed more when opened again from Clarity. This includes finish dates on tasks that have been marked as 100% complete. It appears that the tasks with assignments are working as designed. I've seen this in the past with tasks having assignments, but not tasks with unassigned resources. The date skewing in some instances are years.
What version of CA PPM and which Connector are you using (XML or Legacy)?
We are using CA PPM 14.2 and the XML connector.
Since I believe you have already looked at the obvious possible causes, take a look at these defects and see if you are seeing any of these.
I reviewed the defects referenced and none seems to fit what is happening. The tasks that are set as 100% complete are maintaining that value, but the end dates are moving even though there are actual finishes and no resources.
There are some defects in the MSP XML New Driver in 14.2 (Some referenced above) particularly with MSP2010, so an option would be to try in the Legacy driver and see if the dates stay there. If it is still happening or if you want to troubleshoot more with the XML driver, this will probably need a support case # to troubleshoot further so we can take a look at the XML and the project schedule on a WebEx.