Update 12 Apr 2017: An update has been released that resolves the issue.
Update 06 Apr 2017: We have identified the issue and worked out how to resolve it. An update is being prepared for release.
Original post 29 Mar 2017:
Hi everyone! We just released a tiny update for Subnautica on Xbox One. This update contains no new content, bug fixes, or improvements of any kind. Its sole purpose is to introduce new tools to help us find and fix the save/load bugs many of you have been experiencing. For example, if you do encounter a save/load issue, you will probably now receive a much more informative error message.
We wish we could have released an update with content instead, but never fear, we are continuing to work on new content behind the scenes. Stay tuned to @SubnauticaXbox on Twitter, and sign up to the Subnautica Xbox Mailing List to be notified as soon as the next update is released.