Turntable help

Now that my original hypothesis does not seem to be correct, I would opt for what someone else already wrote: The position in the vertical dimension of the cue-ing lever just needs to be re-adjusted. No biggie.

Lewm -- I read it to mean he's changing his cartridge as a completely separate issue, and while there, he'll ask his tech about the locking problem.   Not that he expects the cartridge change to solve the problem. But I could be wrong......

Dear Phasecorrect,
Upgrading your cartridge is always a fun thing to do, but I don't see how it addresses the issue that you originally raised.  Perhaps you have something in mind that you haven't mentioned here.

How can someone with over 2000 posts not state the model in their post?

Update: arm is in down position when attempting to lock. Im going to upgrade my catridge next week. Sounds look a quick fix for my local hifi tech.

Phasecorrect, When you experience this issue, is the cue-ing lever in the "up" position, as it is when you use the cue-ing device to lift the stylus off the surface of the LP?  If so, then when you swing the arm over to the arm rest, you should release the cue-ing device, as when playing an LP, before locking the tonearm in place. Then the lock is likely to work.  The cue otherwise holds the tonearm slightly above the resting position such that the lock won't easily clamp down over it.  This is common.

Sounds like maybe there is a misalignment between arm tube and arm rest? If so, adjusting the height of the arm rest, or the height of the arm lift,  should fix it. Hard to visualize without pics, or knowing the arm model (at a minimum).