Finally after 4 months of having thousands of subscribers removed from my channel without their permission, YouTube has admitted that there is a problem and is fixing it. Every 24hrs I have all of the subscribers deleted that I have gained in that time, usually more. I have had up to 1412 subscribers removed at once. I have had many complaints from subscribers that they have been unsubscribed without their permission. When some of them have resubscribed, they are unsubscribed again. I have also found other YouTubers, some of them far bigger than I am, who are having the exact same thing happen to their channels. They are even having the same numbers of subscribers deleted at a time, its always 169 or 69, sometimes its random.
Finally two days ago, YouTube sent me the email you see below.