That is typically caused by USB communication problems: a few commands get lost and the remainder come through OK, but at the wrong position due to the missing commands.
A USB cable with ferrite cores seems to cure most of the problems, probably because spending enough to get a cable with cores fetches one with better overall QC. Getting a cable from a reputable brand seems to work better than one from a randomly named Amazon seller also offering beach toys and beauty products.
If the machine is at the end of an absurdly long USB cable, that’s a real problem, because the USB circuitry on the laser end tends to be unqualified for longer cables. An active extender with power injected at the laser end seems to resolve those problems.
Any or all of the USB connectors on the cable / PC / laser may be fatigued from far too many plug / unplug cycles, so if a better cable doesn’t help, the next steps can be expensive.
