Today I've had a few instances of Youtube videos being in between posts, covering other things.
It typically looks like this:
In this case it was this post.
It doesn't happen all the time, it's a random thing. Sometimes the misplaced video will get to the right place after some moments, but this was one of the few times it stayed misplaced.
I heard other members have a problem with ads covering the page, I'm not sure if it is the same error that caused this error. (I do not have problems with ads because I block them.)