The nullable & file rules aren't compatible with each other (if the field is missing from the request, the file rule will trigger regardless of whether nullable is in the ruleset).

I think this is because the under the hood, those fields will arrive in the $_FILES superglobal instead of the $_POST. There is an example of handling this by validating any file uploads separately to the standard fields in the store method here: https://github.com/musimana/bassform/blob/main/app/Http/Controllers/Public/PageController.php (I left it in the controller since it's just an example method, but it could easily be moved to a FormRequest).

If anyone knows a more 'Laravelly' way to do it then I'd love to know!