In the cases you describe it should fail by ruining the print, not the build plate though. If there is something between the nozzle and the plate, it will be too far away from it after calibration, not too close.

Oh I've had my fair share of issues with this. i.e. little specs of the previous print color is stuck on the next print since I missed it during print clean up.

But if I am honest, for a normal spring steel PEI sheet it's perfect. And I prefer this to the magnetic solution like on the Mini since it lets me use Garolite/G10.

I've only seen this issue with the satin bed.

They've stopped using the PINDA probe?

That was the best auto bed leveling system I'd seen because it stood half a chance of ever working. The biggest problem I would see out of them was, well...the whole carriage/extruder assembly was designed by a rock chewing moron.

I used to build and maintain the printers for a little company that 3D printed parts for their products back in the beforetimes, so I've had my fair share of Prusas apart. I don't think I could design a worse mechanism if I tried.

The extruder mechanism was a demented sandwich of parts that don't make sense all made in shiny black plastic so it's hard to see their shapes. You don't build it up from one side to another, you build it up from the inside out. All the wires are supposed to route through a hole in the back of the carriage, then get pinched between the carriage and the extruder body in a couple channels that bend them at sharp right angles. The whole extruder mechanism is a demented sandwich built up from the inside out that doesn't let you easily remove and replace any of the working parts. ANY service to the extruder group, be it a new nozzle, a new fan, a new thermistor, is a complete teardown and rebuild, partially because there are no electrical connectors at that end, all the wires are 16 inches long and run all the way back to the main board. And the PINDA probe mount wasn't a separate bracket that bolts on, it's a feature of the largest, most central piece of plastic and it's attached by a thin little shard of plastic that WILL soften and deform in service.

In the case of a heavily used printer, say for production or a busy prototyping lab, you can't just have a spare extruder built up ready to bolt on and go. You can't have a hot end built up on the bench ready to swap in. If one needs maintenance or repair, it will take hours, no matter how minor the job.

It was like working on a Macbook built by BMW. I didn't charge enough for my time.

Hey, just wanna point out that having a touch sensor built into the nozzle is definitely not unheard of, my printer (Neptune 3 from elegoo) uses the same sensor. It's not the most reliable sensor in the world but it got the job done until I got my BLTouch.