Wordpress upload_mimes not working for front-end uploads of 3D files

Question

So, after the new WP updates my form will not allow certain files to upload. I have a Gravity form with an upload field to submit 3D print files. I can get one type of file to work, but not the others. Just hoping someone else has had this issue and has some update on a solution.

I'm using:

add_filter('upload_mimes','add_custom_mime_types',1,1);
function add_custom_mime_types($mime_types){
    $mime_types['stl'] =  'application/wavefront-stl';
    $mime_types['igs'] =  'application/iges';
    $mime_types['stp'] =  'application/step';
    $mime_types['step'] =  'application/step';

    return $mime_types;
}

Oddly, the .stl will upload but not the others. I have also installed Extra File Types plugin to add file types but no help there. Disable Real MIME Check did not work either.

I also added:

define( 'ALLOW_UNFILTERED_UPLOADS', true );

to wp-config and I can upload these files to the media library as an admin, but I need them to upload from my front-end form.

Answer 1

Thanks to this thread here, I found this code

    function fix_wp_csv_mime_bug( $data, $file, $filename, $mimes ) {
    $wp_filetype = wp_check_filetype( $filename, $mimes );
            $ext = $wp_filetype['ext'];
            $type = $wp_filetype['type'];
            $proper_filename = $data['proper_filename'];

            return compact( 'ext', 'type', 'proper_filename' );
}
add_filter( 'wp_check_filetype_and_ext', 'fix_wp_csv_mime_bug', 10, 4 );

which does allow the files to be uploaded through the form. Not sure what I am opening myself up to, but it works for now.