PLX 1000 - How to solve the arm gap?

I have a pair of PLX 1000 and the two came with a slack in the arms. Note the noise of the slack in the needle, this vibration echoes in the bands with higher bass!
I tried to turn the center bolt to tighten it and see if the clearance slackened, but I noticed that the arm bolts are glued together! Because? How will I regulate this?