It can be pretty much anything. Maybe the two machines also have different versions for the same module, and the interface is different. Maybe the value that is present in one version comes from some input data, like files on the system, the environnement, the name of the user... Maybe the script relies on some undefined behaviour which was documented as unreliable in the doc, and turned out not to be reliable.

It's impossible to know if you don't give us more info. Some of the code where the warning happens would be a minimum.