digital or dial calipers

Does anyone have an explanation as to what would cause this.
Today I drug out a pair of digital calipers put a new battery in them since it seams every time i want to use anything battery operated the battery is flat or if I happened to forget to remove the battery it will be corroded and the tool will be ruined. So it should be of no surprise that i have little faith in battery operated stuff.
But having a caliper read exactly half is a new one on me, also it is repeatable no matter how many times it is switched off and on zero checked then measure anything. The reading is always exactly half and it doesn't matter if imp. or mm.
Attachment 40758

Learnt the hard way that the calipers still draw power even when switched off.

Mine I dropped, so while not showing half, it was short 10mm, even when zeroed, battery pulled out. I removed the screw at the bottom, slid off unit, cleaned and oiled it. After refitting it was working properly. But it was like a man with two clocks not knowing the correct time. I did not trust it so I only use it on non critical measurements.

I learned fussing with the DRO on one of my machines that the display part has a number of different choices for the resolution of the sensor scale, in factors of two in the range it was set for. Perhaps yours somehow got a bit flipped or something inside came loose and the preset is now different.

No clue if you can get to that part to fix it...