Is this still causing a problem in 12.0.6? I've been having a look today and can't reproduce any issues, but there were some fixes to do with sorting recently which could be the reason.
The scriptcolumns.oxc and scriptconfig.oxc both look fine, by the way.
My tests were done with the Custom Column - Newest File script and these two commands:
Set SORTBY="scp:Newest File Column/NewestFile,scp:Newest File Column/NewestFileDate,scp" SortReverse=Off
Set SORTBY="scp:Newest File Column/NewestFile,scp:Newest File Column/NewestFileDate,scp:Newest File Column/NewestFileName" SortReverse=Off