Your main problem is that the CSV file is basically a flat structure, but the security objects aren’t flat at all. The Get-ADPermission cmdlet returns objects of type ADAcePresentationObject. The ExtendedRights property of those objects is an array of ExtendedRightIdParameter objects, and AccessRights is an array of ActiveDirectoryRights objects. Export-Csv doesn’t handle embedded collections well.
Depending on what you need to do with this data, you might be better off exporting it in a different format (XML or JSON), which will handle the more complex structure with less headache on your part.