The input shaping calibration. It prevents artifacts. But don’t forget that’s there for a reason. If you have an AMS on top and you add/remove weight (=spools), it messes with that feature, so I guess that’s why the printer does a short recalibration everytime. I just put the AMS next to the printer (which is anyway on a concrete slab on foam), ran the full 26min calibration once, and removed to code for the short calibration.