Access error 2450 impossible to find a subform "etc, etc, etc,"

Unfortunately this error is notoriously buggy, and occurs in situations and code where it makes no sense. It's possible the error refers to /something else/ but most of the time it doesn't mean what the error title says. I've hit it many times over two decades, and almost never found a rational reason for it (and sometimes, it doesn't even permit a On Error catch). If it occurs consistently, the only way is to rework the code or general concept of the code to avoid having to use the kind of line that causes it (like using Forms(X).HasModule).