I have completed every level and gotten gold time on all of them, but I have not gotten the gold standared achievement. Is this something that has happened to other people? Is there a way to fix this?

have you tried completing every level again? Maybe it has something to do with the new achievement update?

I've seen a few people mention the issue as well, so you're definitely not the only one I'm afraid

I've done the same thing. Is it possible for you to get all of the achievements and fix it? I haven't done it yet, but that could be part of it.