Unable to add multiple groups to a piece of content

It is unclear to me if this is a bug or not, but at the moment I am unable to add multiple groups to a single content type. I have a content type with two entity reference fields which each contain a different group. I can use group A with no problem and same thing with group B, however, if I attempt to put a group into both A and B then I get the following error:
'Drupal\Core\Entity\EntityStorageException: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry'

I noticed this issue was covered in D7 in this thread, but I did not see any mention of it in D8.