Blocked and shadow banned user can still post

Hello! I posted a couple weeks ago about how we're having an issue with a user who is banned from our sub yet somehow he's still able to post. You guys recommend a shadow ban which we did, and it temporarily worked, but now he is able to post again. Before the shadow ban at least grayed out what he had to say but now it doesn't even do that anymore. He's also able to use the mod mail and send harassing messages. I'm not sure what's going on but it's actually getting worse instead of better. The admins looked into the issue and confirmed there is some sort of bug that's allowing him to post but the situation has not improved. I am reposting here for help again. Thank you so much again!