I get this error:

Jun 15, 2022 18:12:28 PM Error [ajp-nio-127.0.0.1-8015-exec-796] - Variable TH_LABOR_CATEGORY_CODE_DESCRIPTION is undefined. The specific sequence of files included or processed is: E:\sites\...\entry\add.cfm, line: 97

but that line number is not part of add.cfm its part of an include on add.cfm:53 WTH! Whats the explanation for this?

When you are using cfinclude to include another cfm page, then that page basically works like it is written inside the parent page. There is no distinction between the parent file and the cfincluded file as it becomes a whole pack.

the stacktrace knows exactly where the error occured, the message and detail should reflect that in my opinion. because as it is its pretty useless.