That app has had to be modified to comply with Youtube's terms of service, so that would appear to be why some of it's functionality has had to disappear. (You can't legally save any Youtube video to any device as it infringes the rights of the copyright holder and breaks the agreement between Google and such rights holders. The use of Youtube, other than for direct streaming from the site, is therefore unlawful; the 'cache' facility was saving content, rather than simply streaming it, so it had to go).