That is certainly not normal. Were you using material with an irregular surface or something that was smooth and consistent? Were they small pieces or were voids in the material where the auto focus in the head snapped rather than on the material? I’m sure curious as to what’s up with your machine.
Trying to see in your posts where you did the Camera Calibration. What were the results?
Haven’t used my calipers to get thickness for material focus since Auto Focus went live. You would still need to buy a calipers though for designing things to get the tabs and slots right. That’s why I bought mine.
The tube being on the gantry is quite a departure from traditional designs. From my understanding, not having to calibrate mirrors or get some type of story stick to get focus height but having a lens that auto focuses has worked out very well for the price of the machine.
Perhaps design and development constraints or trade offs. The usable bed size has been a moving target. Not as big as we expected, but it has gained in size. You can use the whole sheet of material efficiently. Perhaps not at all at once and you may have some margin to discard. And it shrinks with size and speed of engraving. I wasted more materials with the 12x24" from inventables than any of my proofgrade. Always had to make a decision as to how I was going to process it.