Has anyone come across this problem where the FX16, when it is running a program will work fine, but once it is connected to the front end, it may start behaving erratically? OR when the building operator overrides something to turn off (I created an override using a selector switch).

Examples of the FX16 behaving erratically include:

Temperatures reading -300 deg C, when resistance is within range.
Staggered engaging and disengaging contacts (in the case of lead lag operations)
Calibration/Offsets reading an arbitrary number, which consequently affect the actual temperature