Hi.
Truss rod rattles are IMHO the worst. And a sign of bad design/craftmanship.
Luckily there's a cure, sort of, if You're adventorous and the problem is really bad

.
On single acting rods, take the truss rod nut off and with a syringe and a needle, fill the truss rod cavity with silicone sealant or something similar. You'll probably have to use at least 4" needle to reach far enough.
On dual acting rods, either take a fret off (8th or so), drill a hole in the middle of the slot and fill the cavity through the hole, or just drill the hole through the FB and fill the hole later. Here You can use ~1mm drill and needle, quite invisible.
Quite extreme, some may think, but it works. And less expensive than taking the FB or skunk-stripe off.
Regards
Sam