Error – Invalid membership level ID

We are setup with Stripe for registration against a specific membership level. Normally this works as expected, but on occasion the user get an error message after they complete the registration process ( Form builder add-on). If we check the new member in the backend everything is correct and the membership id has been set, so it just the messaging is confusing to the users. Any idea what is causing this?

Error! Invalid membership level ID! This membership level does not exist. You may have deleted this level. Check the membership level ID and correct it.