So that error doesn't exist in MessageBird? I don't get it. Is it not dependent on carriers as well? I'm asking how they technically do things differently that would absolve them from encountering that issue.
When you connect directly to a carrier you get so called PTT codes back (industry standard). Not all carriers do this the same way but we standardize this and return them like shown at the link below. When your provider uses a lot of in-between providers its harder to return errors correctly. https://developers.messagebird.com/docs/smserrorcodes