Can DT look for and recognise duplicates in Indexed folders?

When I add the same document manually twice to the same DT database, it recognises it as a duplicate. BUT, when this document already exists in an indexed folder, then it does not recognise it as a duplicate - even after forcing a re-sync of the folder?
Am I doing something wrong or is this not possible?

Which version are you using? Since version 2 indexing/importing shouldn’t make a difference (and I’ve just checked this using a plain text document).

Version 2pb7. But now it seems to be working!
These are Sente renamed PDFs in a folder managed by Sente and Indexed by DTP. The only thing which changed is that I redefined the renaming template to make less likely that two different pdfs/papers could have the same file name.
Anyhow, thanks for the quick response