As I recall, you have to access the screws tightening the vertical strip from the opposite side of the column. There should be access holes
directly opposite each one, though I can't remember the screwdriver size. I should have a full manual somewhere, but it might be hopelessly
buried in stacks of ancient literature. You might be able to download a copy from the Jensen Optical website (Durst Pro USA). It also helps to
clean and lube the big feed screw connected to the locking knob in front of the baseboard. Basically, you might need to inspect all the interconnected mechanical components. But a good tuneup should last a long time.