WordPress Failure Notice After Upgrade to 4.6

NSFW

After upgrade to 4.6, my site stopped functioning properly. I made a post, published it, looked at it, but noticed that featured image was not set despite knowing I set it. I went to edit the post again, but got the “WordPress Failure Notice” message.

By going back to Posts, I noticed the post is not there. Since then, I tried to make a new post, but since autosave wouldn’t conclude to generate the URL, I hit Save Draft, only to get the “Are you sure you want to do that?” page.

Is my site eternally screwed now?