what's causing a SME 3 to stick after a few spins?

Check that the arm is not touching the arm lifter bar during playback. If the arm is not horizontal but sloping up from the cartridge to the pivot point, this can happen during playback

That sounds right but when I lower the arm in the space between the arm rest and the platter it drops a few mm below the lp surface. Thanks anyway

How hard is it to push the arm across the platter in the raised position? Or does this "locking" only occur when the arm is down at the record surface level?

> Does this occur with the AS turned all the way off?
> When it 'skips', does it skip toward the center or outside edge of the record? Or rather, by 'skip', do you mean it won't track (keeps playing the same groove over and over again?)
> What Sutherk asked -- does it resist horizontal travel when the stylus is slightly above the record. You can check this by looping some thread under the TA wand near the headshell, and with the lifter down, AS off, stylus guard in place, hold the thread in one hand suspending the cartridge end of the tonearm just above the platter, and holding the thread, try gently moving the arm across the platter in both directions. If the horizontal bearing is seizing, you'll know right away. Are you the original owner?
> As far as I know, the only silicone damping in that arm is in the lifter mechanism, and the swiveling DIN plug. So I can't see how any would get into the horizontal bearing?

The problem occurred when I first hooked up the turntable after arriving from Fed Ex. It eventually improved and then returned after I adjusted the overhang. This mis-tracking went away also and now seems to be working just fine.
By skipping I mean it gets stuck in the same groove. When I raised the arm and and gently pushed it towards the spindle I did feel a little bit of resistance.
I'm not the first owner and the person I bought it from wasn't either but says it was set up professionally.
I'm going to change the cartridge and see if the problem returns.