I was not aware of this fix until this morning so am passing it on for others that might not be aware.
Probably a coincidence that all 3 of my calipers went gunnybag at about the same time and I was beginning to think that it was some conspiracy crap having to do with solar flares . Finally got the gumption to google a remedy and found a fix.
* The problem: erratic readings, switching from mm to inches erratically and a number of similar issues.
* The fix: disassembly, attach a piece of tape and re-assemble. Way easy and still in shock that it worked on all 3. The link to the explanation. Use at your own risk, ymmv.