So I've been printing some pieces that have very exact size requirements over the last couple of weeks. And the Mini has been doing very good.

But today, all the prints I've tried have been too small by varying amounts. Anywhere from 0.15mm to 1.9mm.

I tried a 20mm x 20mm x 20mm cube as a calibration: It came out as 19.21mm x 18.3mm x 21.4mm.

Seriously, WTF is going on, and how can I fix it?

Updated info:

Printing PLA, same roll I've been using all week, Digistruct White, no tangles at all, opened the vacuum seal on Tuesday.

Printer hasn't been moved from the spot it's in since I got it, back in August. Temperature and humidity haven't changed more than a degree or two.

It's the same .gcode I've printed from before with no issues. Re-sliced it anyway (same slicer I've used before with no problems) as a test.

NO settings have changed at all.

Re-leveled the bed on Wednesday and did the usual weekly checkover. Everything is nice and tight where it needs to be tight, all rods move smoothly.

Update 2: Printed another 20 x 20 x 20 cube, and got 19.4 x 21.2 x 18.7 this time.