Flying Kiwi

i got it working, what i changed is the following:

changed the add_permastruct args-parameter to include a endpoint-mask:

add_permastruct('mline_products', $permalink_prefix.'/'.$permalink_structure, array('with_front' => false, 'ep_mask' => EP_PRODUCT));

also changed the post-type-link filter to only do stuff for the custom-post-type with the custom permastruct. (dno how i could have missed that earlier.) Not sure if this had something to do with the problem i had.

function mline_cpt_products_permalink($permalink, $post) {
	if(('mline_products' == $post->post_type) && '' != $permalink && !in_array($post->post_status, array('draft', 'pending', 'auto-draft')) ) {
		$rewritecode = array(
			'%prodcategory%',
			'%mline_products%'
		);

		$prodCategory = '';
		if ( strpos($permalink, '%prodcategory%') !== false ) {
			// get the genre:
			$terms = get_the_terms($post->ID, 'prodcategory');
			if( is_wp_error($terms) || !$terms ) {
				$prodCategory = 'uncategorised';
			}
			else {
				$prodCategory_obj = array_pop($terms);
				$prodCategory = $prodCategory_obj->slug;
			}
		}

		$rewritereplace = array(
			$prodCategory,
			$post->post_name,
		);

		$permalink = str_replace($rewritecode, $rewritereplace, $permalink);
	}
	return $permalink;
}
add_filter('post_type_link', 'mline_cpt_products_permalink', 10, 2);