Custom search by date_add -> no results

[Scully]

according to different posts, I changed product-sort.tpl to add an additional sort criteria (date added) like that:

 

            <option value="date_add:desc" {if $orderby eq 'date_add' AND $orderway eq 'desc'}selected="selected"{/if}>{l s='newest products'}</option>

 

This works fine, when browsing trough categories and then changing from default sort to newest products. However If I enter a search term and then choose the drop down to 'newest products', I get a messed up result without images, whithout text and only one hit over all.

 

Shop URL: WIR-Shop

Search term (example): Siemens

Found products: 104

 

Sort by last drop down entry (neue Produkte) - result messed up

Sorting by any other field - result is OK

 

Any help is appreciated. Scully.

 

 

 

Edited August 20, 2014 by Scully (see edit history)