If your YouTube Subscribers disappear in large numbers this is not because of unsubscribers. The public count may go down but the users are still subscribed to you and will receive notifications when you post new content. What occasionally happens is that if you gain Subscribers too quickly then YouTube's automatic system may flag them as spam. Every channel will have a different threshold for this. You should play with your Payout to find the right promotion speed for your channel.
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