Hey its still the same PHP Warnung with the new version:
PHP Warning: Declaration of action_plugin_issuetracker::register(&$controller) should be compatible with DokuWiki_Action_Plugin::register(Doku_Event_Handler $controller) in <path>\dokuwiki\lib\plugins\issuetracker\action.php on line 3776
I do speak german, but I cant find a hint how he solved the problem. We'll see, I've asked him about that.