Extra “uploads” added in path

Resolved in a completely different way. Googled this, so technically not my own answer, but does the job:

// ACF upload prefilter
function gist_acf_upload_dir_prefilter($errors, $file, $field) {

    // This filter changes directory just for item being uploaded
    add_filter('upload_dir', 'gist_acf_upload_dir');
}

// ACF hook, set to field key of your file upload field
add_filter('acf/upload_prefilter/key=field_5b2b0326ea0e1', 'gist_acf_upload_dir_prefilter');

// Custom upload directory function, trigger by prefilter
function gist_acf_upload_dir($param) {

    // Set to whatever directory you want the ACF file field to upload to
    $custom_dir="/uploads/member-files";
    $param['path'] = WP_CONTENT_DIR . $custom_dir;
    $param['url'] = WP_CONTENT_URL . $custom_dir;
    return $param;
}