I entered a range of zip codes and the selected records were duplicated. How do I go about reporting the issue to have my request analyzed for an error on my part or get bug fixed?
Your question suggests you're using the Zip Code Range custom search - but this is a very old way to handle zip code range searches, from before Advanced Search could do them (10-12 years ago). In my opinion, this search should have been removed a long time ago, but that's an issue if someone has a smart group built on it.
The more-modern (though not most modern!) way to do a zip code range search is Search menu » Advanced Search. Check the Range box (see screenshot) in the Address Fields above Postal Code.
The most modern approach is to use Search Kit, but despite being more powerful than Advanced Search, it's also got a steeper learning curve, so I recommend Advanced Search for now.