Okay I’ve found there are errors, when the script is loaded:
[02:30:58.351] Use of getAttributeNode() is deprecated. Use getAttribute() instead. @ https://www.####.de/wp-content/plugins/podpress/js/jquery/jquery-1.4.2.min.js?ver=3.5.1:48
[02:30:58.351] Use of attributes' specified attribute is deprecated. It always returns true. @ https://www.####.de/wp-content/plugins/podpress/js/jquery/jquery-1.4.2.min.js?ver=3.5.1:48
[02:30:59.778] SyntaxError: JSON.parse: unexpected character @ https://www.####.de/wp-admin/load-scripts.php?c=1&load%5B%5D=jquery,utils&ver=3.5.1:2