Koxx Longneck Frame

It sounds like Gilby’s analysis is the most likely one, although you may also check that the bearings haven’t slipped to one side.

The Sem XL frame models are very good frames, amazing for their inexpensive price. They are excellent stiff steel with a fine crown design, and have worked very well for many years now. Their chief weakness is that one often needs to shim a leg with 1-3 can thicknesses. This is a minor irritation when one considers that they are 1/6 or less the cost of a custom frame. Until Sem came out with the XL Longneck 3-4 years ago the only option was a Wyganowski custom at $400. They have withstood the test of time well.

Chances are very good that another frame of comparable cost would have the same problem, with the chance for other complications. For example, the Sem XL frames are a cut above the Yuni line for overall quality, in my humble opinion.

I own and have built/sold unicycles with Torker, Sem XL, Sem XL Longneck, Pashley, Yuni, GB4, Hunter, and other frames, so this is the context from which I speak.

An aside:
This thread and its companion thread are about the process of troubleshooting, a skill which, should one be diligent and lucky enough to become proficient at it, can make one lots of money in electronics, software, insurance, management, etc etc etc. It’s kinda dismaying how fast it degenerated into personal attacks. CEOs and their employees make huge amounts each year troubleshooting software race conditions, satellite communications throughput, spacecraft warning lights, stuck rods in nuclear power plants, underperforming retail locations, high management personality conflicts, international relations, financial crises, and the like. An open mind and eye can pull a lesson from just these two threads that, someday, may make that person stand out in a job interview or even in the field on the job, and earn them a well-deserved raise, position, or reputation.