Is Maple Syrup with Scum on Top Still Safe to Use

Dear Milk Street,

I really enjoy your podcast, thank you.

I am trying to remember where I heard that maple syrup can go bad, and I do listen to Milk Street quite often. I had always heard that it couldn't. I asked my maple person and she hadn't heard anything about that new fact, but wanted to know more about it. And now I can't remember where I heard it, but the next jar I opened happened to have a small layer of scum on the top, so I was trying to decide whether to use it or not. She did say that they had an issue with some bottles not sealing because of a temperature gauge problem. But if I knew it was fine I would go ahead and use it. Just curious.

Thank you,

Pam