Skipping is one of those issues that can have a few different causes, and it's worth understanding what's actually happening mechanically when a record skips, because the fix depends entirely on the cause. We're going to cover the main cutting ones we see, and the main take away is to always use a microscope to diagnose, it is the only way to actually see what is physically happening. This is all assuming your playback stylus is weighted correctly, but for now, we will only cover cutting issues.
GROOVE DEPTH
Groove depth is probably the most common cause of skipping on lathe cuts, and it ties directly into something we talk about a lot, if you don't know your actual groove depth and only using weights, you're guessing. A groove that's too shallow simply doesn't have enough depth to contain the modulation properly and can even break if the blank has any warping.
OVERCUTTING
Grooves colliding (overcutting) is a volume versus pitch issue. On a fixed pitch system your groove spacing is set, and if you're cutting too loud the lateral excursion is moving widely that they hit into the previous groove. When the playback stylus hits that point, it gets knocked sideways into the next groove and skips. The fix is either to reduce your cutting volume or to widen your pitch spacing to give the grooves more room.
PHASE
Out of phase audio is a less obvious one but worth understanding. When audio is out of phase, the difference between the left and right channels creates excessive vertical modulation, as we've covered in our M/S post, vertical modulation is the up and down movement of the stylus. In severe cases, this vertical movement is so extreme that it physically lifts the cutting stylus out of the groove during cutting. The result is a section of the disc where the groove is either very shallow or essentially disappears, and the playback stylus has nothing to track. This is why phase correlation is checked during mastering.
VACUUM SYSTEM
From time to time people we have customers leaving swarf in the groove, where the vacuum system has not collected it properly. The other thing could be dropped swarf during a cut knocking the diamond stylus. Always triple check all vacuum system joints for air leaks.