Resolved; replaced problem row with this:    "'" + $Row.$Prop + "'" 

Also needed to modify these rows:
$Insert = $InsertValues -join '), ('
$InsertQuery = "INSERT INTO $DestTable ( $( $Properties -join ', ' ) ) VALUES ( $Insert )"
Invoke-Sqlcmd -ServerInstance $DestServer -Database $DestDatabase -Query $InsertQuery
To this:
$Insert = $InsertValues -join '), ('
$Cols = $Properties -join ', '
$InsertQuery = "INSERT INTO $DestTable ( $Cols ) VALUES ( $Insert )"
Invoke-Sqlcmd -ServerInstance $DestServer -Database $DestDatabase -Query $InsertQuery
This code runs correctly in the ISE & in the SQL JOB.