Brand new 716's? Since they were introduced in October of 2015 and sold new until late 2017, they would be uncommon at this point.

Assuming they are not counterfeit, Titleist does add weight in the hosel (hot melt or lead), so it could be that the added weight has come loose. That this occurs with 4 irons would be unusual. You may want to have a local pro shop work with the local Titleist rep to see that these are legitimate. Since you just purchased old inventory new, you should be covered by the year of warranty from purchase. If covered, Titleist may repair or replace at their choice.

Yes. They're definitely not counterfeit. Besides the fact that they're lefty, it was a set a local shop had from a previous order that fell through. Got them at a price I couldn't say no to

At best, they have been sitting somewhere for over 3 years, maybe even longer. The first 716's were available late 2015. The 16 in the 716 number is the year they officially released that model. Since then, they produced 718's and now T-series. If they sat for years in a harsh environment in someone's stockroom, the epoxy could be breaking loose inside the shaft. Titleist makes sets to fill orders so they would not have had them in some wearhouse, they had to be stored at a source. Hopefully they came from a reliable source and are not counterfeit. Not much you can do if they are counterfeit. If they are real, they are still long out of warranty from Titleist and only the seller can help you at this point or you can take them to a repair service and see if they can resolve the issue. Sorry. Hate to be the bearer of bad news. Hope you get them fixed and it turns out to be something minor. You sure don't want the heads to start flying off during play if it is an epoxy problem.

Thanks for the answer! Definitely was a reliable source. You mentioned the epoxy in the shaft. Would a possible fix be to get them reshafted?

If that indeed turns out to be what is creating the noise. You might have one club done and if it really does turn out to be loose excess epoxy, have the rest done or decide just to live with it. If it is epoxy that is in the shaft, you can pull the grips and bang any loose pieces out the grip end of the shaft without having to remove the entire shaft. Might be worth a try. Good luck.

Club pic for reference as some were mentioning it could be a counterfeit