Hi CarlosI210! How ya been?
Corns definitely rattle when pissed! (Maybe not only then, but I know that's one of the times they do!)
I know this because one of my adult corns (Lilly), the female of the trio I have (also have a young, unsexed one from a clutch Lilly put out last spring). She rarely does it, and only when she's stressed or as I put it, pissed-off! I never intentionally get her to that point , of course, but sometimes when I used to take her out of her hide for feeding (when I could tell she didn't want to come!), she'd scurry to the back of the viv and as my hand approached her, sometimes I'd hear that rattle as her tail thumped with a furious frequency against the side of the enclosure! Scared the HELL outta me the first time I heard it! Probably the result she was looking for though! I mean, it worked because I backed off!
If it's during feeding, maybe it's just the adrenaline they assign towards the hunt usually associated with food(?). Don't know. Are you using live rodents? Maybe an expert here will chime in. Though I've had my corns for a little over 8 years, I'm in no way near an authority, so I even may be wrong about the reason they do it, just know that corns can and do rattle on occasion!
Hoped that helped!