One of the parts on Omega B-22 and B22XL enlargers that may eventually require replacement is the focus rod. What typically happens with heavy use and/or lack of proper lubrication is that the rail becomes worn in one area, which results in the focusing becoming loose in that area. The focus mechanism will eventually start to slip in that spot. If you add tension to the focus mechanism to compensate for the wear, focusing becomes excessively stiff in the other areas. The best solution is to replace the worn rod.
These replacement focus shafts are used and may have cosmetic marks from previous installation, but they have been rebuffed and are in perfect working condition.