This isn't really a bug or glitch, well maybe a glitch, but anyway, this wasn't found out on AEM it's happened on a different server. K anyway. So there's a way you can exploit your mining level with a few vanilla items, I don't know whether to go into detail, but I can PM a staff member how to do it so they can possibly patch it. All it does it let you mine placed blocks over and over and still level up your mining.
I mainly don't want to explain how it works on this post because if players see it, they'll try it and stuff.
Have you try it on Aem to make sure it's 100% working? Sometimes it works on other servers but not here. Feel free to leave a private message about this. Thanks for the report
