VPI 3D arms can warp, crack (it happened to me). Your post doesn't sound like you are trying to rotate the rear weight.... If this is as you describe, contact Marc at VPIindustries.
VPI Prime 3D arm making noise
So I’ve been fighting sibilace with my new Soundsmith Carmen mk2. Today while examining my tonearm I was holding the arm with my left hand rotating it and I heard a creaking sound! I put my ear to the pivot housing and gently rotated the arm between my thumb and forefinger and sure as day a creaking sound could be heard. It’s as if the tonarm shaft, where it meets the pivot body, is some kind of friction fit and these pieces are moving independently of one another and making this noise. Understand that the counterweight is still on the arm so there is a bending force being applied to the arm while I rotate it. Thing is, I thought the whole arm was printed. Is this not correct? I’ve contacted Music Direct and left a message. Hope to hear from them tomorrow.