INA126: Why output of INA126 is going to 2.5V when Non-Inverting Terminal (Ground) is lower than inverting terminal (1V)

Hi,

As per below schematic, we supposed to get 0.7V at the output of INA126U, but we get 2.5V at the output in some of the lot of INA126U. May i know why do we get a different result and why not some other voltage like 1.5V or 1V.