The reason ausman and I think others can't get a handle on what happened is because we don't have the whole story.
My idea of what happened, and even that doesn't add up completely, goes like this:
When the guy cam in to replace the short z sensor cable in side the head, he broke, bumped it wired a switch incorrectly. The z sensor internal wire is right next to two switches on the very bottom of the cutting head. One of these switches tells the control the cutting cone is on, the other tells the control that the 10" lens adapter is on. As I previously stated, which no one read, the ten inch lens adapter off sets the z axis by 2.5 inches making the stroke length that much shorter.
So, to put it all together... The program starts, the head starts to comes down, the control looks at the " the thicknesses " adds one inch to that number and turns on the sensor. Now, the z axis is offset by 2.5" because a mechanic is not careful, plus the standard one inch, plus the thickness and turns on the sensor and traveled very slowly downward looking for the material. (How many times have I typed this?)
The part that is missing, and I am not sure how or why it's missing. At some point the machine should have generated a "lens not correct" alarm. I can not imagine how the mechanic could have bypassed this function/error code.
My point is, not the machine's fault, mechanic's. I hope no one got charged for the service call.
My other point. I like helping people out. I like to think I know a thing or two about these machines. If I am going to keep contributing, give me a damn purple star, read what I write, if you don't understand, ask questions, do the experiments I propose unless you think you are really going to break something, report the results. I am paid professional, just not by the forum.