Ok, so it turns out that this was caused by a problem in my stepper motor drivers, which results in missed steps, as described on this guy's blogThe fix was to hook up these "TL Smoother" modules (I got these particular ones from amazon but there are a bazillion clones)After hooking up TL Smoother, this is what the print looks like: ..

This site survives thanks to advertising. Disable AdBlock to see the whole correct answer at no cost!
We promise you will not find boring advertisements. Find out how to disable Adblock by clicking on this link.
Remember to update the page once you have disabled it.

Or consider yourself a bad and cruel person 😢 and look at the answer anyway..