@droftarts @chrishamm Good news! I just managed to finish a 4.5hr print, which came out flawlessly 🙂 I'd never been able to print that long without a failure, so I'm hopeful that's the end of that!
Edit: And I've now finished a 12hr print as well!
Perhaps the wires I moved (for the 5V inductive probe, IIRC) were somehow triggering the reset button through EM interference?
Oh, and for good measure, I ran M122 after the print finished, and it reported TfrRdy pin glitches: 67. Hopefully that won't be a problem in the future, but I suppose I can always try a new ribbon cable if it comes to that.
Thank you both for your help! 🙂