Get the redding dies, that will fix it, I'd bet a bag of donuts on it.
Im not a big fan of collet dies to beging with. After spending hours turning necks and then use collet dies to crinkle the necks back up seems redundant. Bushing dies will smoothly reduce the neck diameter without chewing up the necks.
Ive made an observation that my necks split sooner if Im using collet dies regularly.

Get the compatition Redding die set and you'll be very happy. If you want extream precision, get the redding compatition die set in 280rem and then use your chamber reamer to ream out the dies for even better concentricity.