找到了一条命名路由，但匹配失败

I have a strange problem with cakephp 3 and named routes.

  foreach ($categoryProducts as $key => $categoryProduct) {

    /**
     * WORK
     * Result : http://www.website.com/shop/slugshop/products/slugcategory
     */
    $categoryProduct->href_shop_view = Router::url([
      'slug' => $shop->slug,
      'category' => 'some_caractere'.$categoryProduct->slug,
       '_name' => 'viewShopProductsByCategory'
     ]);

    /**
     * Dont't work
     * Result : A named route was found for "viewShopProductsByCategory", but matching failed. 
     */
    $categoryProduct->href_shop_view = Router::url([
      'slug' => $shop->slug,
      'category' => $categoryProduct->slug,
      '_name' => 'viewShopProductsByCategory'
    ]);

  }

And in my routes.php

Router::connect('/shop/:slug/products/:category',
     ['controller' => 'shops','action' => 'products'],
     ['slug'=>'[^\/]+','category'=>'[^\/]+','pass'=>['slug','category'],'_name' => 'viewShopProductsByCategory'
   ]
);

Can you help me please, because i don't found the solution yet and i don't understand my mistake...

Thank you for your help

Edit 1

@ndm Like you can see i use the same named route, with same shop slug and category slug.

But it's like if $categoryProduct->slug return nothing if you don't put somme caractere before

Edit 2

debug($categoryProduct->slug); // Return "e-cigarette"
debug($shopp->slug); // Return "vapoton-com"

If i write directly :

$categoryProduct->href_shop_view = Router::url([
  'slug' => 'vapoton-com',
  'category' => 'e-cigarette',
   '_name' => 'viewShopProductsByCategory'
 ]);

It's work !

Thanks for your help