Heads up, this rollout opt in does introduce limits on Attributes Per Instance: I cover this a bit here.
That being said, it’s not great that the error messages are extremely unclear as to what the error is and we should fix this. Will get this in our triage list.
Hey, did you try to set an attribute with a long name (> 50 characters) in Studio UI? Or you were setting more attributes than we allowed (64).
I think if you change value of attribute and that change exceeds the limit, you will get a more helpful message. It can be counter intuitive that it only gives a general message when you are adding a new attribute.