Focusing adjustment is too tight on field camera

Could this sticking be due to a change in local humidity causing the wood to swell?

I've had this on my Ebony and in fact, the manufacturer suggests a couple of strategic screws on the geared plate are slackened or tightened accordingly in the event of binding.

Rather than a silicone lubricant, i would suggest natural beeswax.

Mike

Thanks to all for your insights and suggestions. I'll do some more checking, but this is getting beyond my very limited engineering skills -- a term that would incite instant snickering in my dear family, who have seen the products of my skill many times. I'll probably have to save up, again, and send it to Richard Ritter, who knows from the inside how these things are built.
Just when I thought is was safe to go back in the... field.