Lookup Fields in Access are problematic, and you've just surfaced one more reason to be suspicious of them in Access.
Search the internet, and this forum, for posts on the problem that is Lookup Fields in Access.
In Dataverse, the equivalent field will be "Choices" or "Choice" ( I can't recall off the top of my head if the name is singular or plural).
This calls for some fix-up on your part, in the Dataverse environment. It's possible with enough digging around to find how Dataverse expects you to do it.