[Mooff]

Ah i see, the issue seems to be my version of equalizing the preview text length (which i changed numerous times along the way). Thought it would work for everything since it does work with the german special characters ? ? ? and so on.

Anyways, quick and dirty fix would be removing the equalizing part (preview length then might differ depending on how many special characters are in there, but everything should look fine then)

again, untested

                /*remove everything from the previewtext - html and bb. I do not want bold or colored text there. Cut to a decent length.*/        
                $article['pagetext'] = strip_bbcode($article['pagetext'], true, true, false, true, false);
                $article['pagetext'] = strip_tags($article['pagetext']);

                $article['previewtext'] = str_replace('<br />', '', $article['pagetext']);

                $article['previewtext'] = html_entity_decode($article['previewtext']);
                $len = $description_length;
                if ( strlen($article['previewtext']) > $len )
                {                    
                    $article['previewtext'] = substr( $article['previewtext'] , 0 , strrpos( substr( $article['previewtext'], 0, $len), ' ' ));
                }   
                $article['previewtext'] = htmlentities($article['previewtext']);

changes into

                /*remove everything from the previewtext - html and bb. I do not want bold or colored text there. Cut to a decent length.*/        
                $article['pagetext'] = strip_bbcode($article['pagetext'], true, true, false, true, false);
                $article['pagetext'] = strip_tags($article['pagetext']);

                $article['previewtext'] = str_replace('<br />', '', $article['pagetext']);

                $len = $description_length;
                if ( strlen($article['previewtext']) > $len )
                {                    
                    $article['previewtext'] = substr( $article['previewtext'] , 0 , strrpos( substr( $article['previewtext'], 0, $len), ' ' ));
                }

--
your other question.
The slider can handle that.

If you edit an article the next time the cms widget cache runs out the new version will be in. By the way i would strongly advise to use the widget cache on this one. Default setting there is 5min - the widget cache for the slider refreshes every 300 minutes on our website. Using the cache the load time is blazing fast. Letting the database query run, sort the articles and then resize and save a bunch of images is not so fast.