Two files open with same field names causes changing calculation scripts?

It was hard to write a concise leading question for this one... I create and manage files for several different companies. These forms are often similar in structure, and often have many of the same field names.

For example, both Companies A & B have two different locations. The user selects a location by choosing a radio button. The field "LOCATION_NAME" contains a script that displays the name of the location dependent upon the radio button selection.

Yesterday I happened to be working on both forms (two separate files) at the same time. I was testing out some code and noticed that Company A was showing location info from Company B. The script for "LOCATION_NAME" in the file for Company A, had changed to the same script as Company B.

Is this a known issue? I've been working on forms in this manner for years and I've never had this problem before.