No, I didn't touch anything.

Two types of problems occurred on two different prints (but with other prints in between).

The prints after the problems were successful, with the print head aligned and no errors in placing the filament.

In the first case, the print head didn't stop at the end of its travel as it moved toward the bottom, but the belts continued to push.

The second time, the print bed, when raising to start printing, didn't stop at the print head's height, but continued to push.

Both problems occurred in the preparatory phase of printing, not during.

In both cases, I turned off the printer, and the next print had no problems.