Everything was printing OK until half-way through today, for no apparent reason I started getting “moth-eaten” prints.
I tried re-calibrating and squishing down a little more but it didn’t change a thing. I cleaned the nozzle, and wiped the bed. All the settings are as per normal. What’s the problem?
I finally broke down and squished down a whole lot more, until I was getting perfect right angles at the corners of the “First layer calibration” pattern. That subtracted an extra 0.12 mm from the bed, and seemed to improve things a lot.
But there are still apparently random things going on that I don’t yet understand.