I think it picked up a speck of lathe swarf and got a scratch across the sensor wires. It felt gritty suddenly and then blanked out when I was turning an SS powder-thru insert, then gave an error message and after that wouldn't even turn on. Swapped batteries and cleaned it to no avail. I've used the crap out of it for right at 20 years and it had a pretty hard life as a mechanic's tool, then as a gun room do-all, and most recently as a lathe accessory. I'm still searching for a good replacement, looks like Mitutoyo is the thing now. Got a cheap-ish "large print" set that also can display fractions to hold me over.