You hit publish, you're happy, and ten minutes later your subscriber count goes down. Is it your fault? A YouTube glitch? In March 2019 I explained why it's neither, and why it can even be a good thing.
It's not a bug
No matter how expensive your gear is or how much effort you put into a video, as soon as you upload it you're going to lose a few subscribers. It isn't a glitch or a YouTube bug. People get your notification, maybe open the video, realise they're no longer interested in your content, and unsubscribe. Some probably subscribed by mistake or didn't really know what the button meant. The more often you post, the more chances there are for that to happen.
Think of it as a weekly clean-up
I used to get really annoyed about it. Now I see it as positive. Those were inactive subscribers: they weren't watching or engaging, they were just a number. What you're really trying to do with each upload is attract new people who are interested in what you do and who will comment, like, watch and share. Whether you have 1,000 subscribers or 100,000, it happens to everyone. If you don't lose any, even better: it means your audience is committed. Either way, keep creating.