Symptoms
After performing the 4.6.9 > 4.7 upgrade, K2 does not pull users from a SharePointgroup on a claims enabled site.
Diagnoses
This was working before the upgrade to 4.7, and because of that, this was diagnosed as a "breaking change".
Resolution
We gave the client a fix and after applying it to the staging and production environment, all was well and we were able to get users from a SharePoint group on a claims enabled site as expected.