It's possible that this was introduced in CORE-5262. When searching for a domain on the order form, if there are active and inactive packages for the TLD, it may return duplicate results.
To reproduce:
1. Set pricing and activate a TLD under Packages > Domain Options, in this example .com
2. Add a domain to a client account that uses the registrar module set for the TLD.
3. Change the TLD to another module under Packages > Domain Options.
4. On a Domain and Other order form, search for a domain that should be available, in our case blestacularly.com by entering "blestacularly.com" in the search box without selecting any TLDs.
5. Note that blestacularly.com is show to be available, then another record is displayed, and finally a third, the 2nd and third loading via ajax. Sometimes it's necessary to click the "Load More +" button to see them.
See screenshots.