Date Changes on Copy out, each time it is run

Earlier, the code shown below would faithfully copy out the files in a given folder with a given search spec.

Then something changed... and the date-time on the files now increment to the time the PWPS script is run, rather than showing the date-time as shown in PW.

Each time it runs, the date-time updates to current, it does not skip files as "up-to-date".

$result            = Open-PWConnection -DatasourceName $Datasource -SSO -Verbose
$files             = get-pwdocumentsbysearch -FolderPath "$ProjectWiseFolder" -JustThisFolder -Filename "$FilenameString"
$result            = $files | CheckOut-PWDocuments -NoReferences -RemoveCopies -Verbose -CopyOut -ExportFolder "$ServerFolder"

Ideas?