It can be one of two things. It can be loose epoxy in the bottom of the shaft or the backplates can be loose. If it’s the backplates, you might want a golf shop to add a little more glue to keep them from coming off during play. You can tap on the backplates and tell if they are what is loose. As for the warranty, most golfers play frequently and some are a bit rough on their equipment. A warranty that went beyond a year for those golfers would be problematic. Oh, and most car warranties are also tied to years, not just miles and most automobile drivers do not off-road 100 percent of the time. :)

Could be the back plate coming loose. I had the same thing happening with my T350 5 iron recently. I tapped on the back plate a few times and could tell it came loose. When I got home I gently pried it out and put a bit of epoxy in place and reset it. Good as new.

Likely dried epoxy that has come loose and is either inside the head or in the shaft.