I have compared the field keys through admin and they are indeed correct.
I found this in the documentation for get_fields():
This is a very simple function which finds ALL custom field values **(that don’t start with an “_”)**…
But i have both with and without _ stored. I assume that’s normal, but i don’t understand why it returns the wrong data. It works just fine everywhere else, it’s just for this specific field group it messes up.