thank you for contributing your knowledge to the forum.
I believe that only viable solution to get higher accuracy is to use something like RedCatch GNSS-RTK add-on.
Where did you find that the THETA X uses the uBlox ZOE-M8B?
I searched on this blog and the spec sheet for the THETA X, but could not find reference to the GNSS chip used.
Reference
more detailed post by JoscTr on this subject.