Recently when inking the rollers on my Vandercook SP20 I have encountered the following problems. 1) When I apply ink across the distributor roller and let it down on the form rollers the ink does not spread evenly and there seems to be some hesitation in the distributor rollers. 2) When I roll the rollers over the form the distributor roller does not roll or seem to be engaged. and 3) when I return the rollers to the inking position the form roller that makes contact with the inking cylinder jumps out of its support bracket and is no longer in contact with the inking cylinder.
Often there are multiple defects.
It is likely that the form rollers are significantly undersized, their diameter should be 3″.
The worm gear and crescent probably need to be cleaned and lubed with Vaseline. Hesitation can be caused by excessive grime, which in turn can cause a broken gear or crescent. Inspect the points on both.
The support brackets are bent allowing the rollers to jump and skew.