With the 6690 version the thumbnail don't display if use a Xhmaster video. To resolve this problem edit ow_plugins/video/classes/video_providers.php in line 499 replace

$url = isset($match[1]) ? $match[1] : VideoProviders::PROVIDER_UNDEFINED;



with

$url = isset($match[1]) ? urldecode($match[1]) : VideoProviders::PROVIDER_UNDEFINED;