This is a very simple part that has had multiple copies and pack-and-go's made over several years.

The part consists of four imported bodies.

Now just one of those bodies has the error "external model could not be found" and is not visible.

The missing body does not point to anything. There is no "external reference" option in the feature tree.

Clicking on File > Find references, only refers to the file itself.

Strangely, if I open in 2023 Solidworks, the part displays fine, no errors. Even if I press the refresh button.

But if I press Ctrl-Q the problematic body disappears and the error is recreated.