My first suggestion would be to create appstacks with Office 365 installed into the sequencing machine (I know people say otherwise, we just use the golden image and clone it for our packaging machine).
I have seen funcky stuff regarding mostly licenses that even though we didn't install anything related to Office (it was RSAT in our case) there was still license information in that appstack.
You could also (with 365 in the sequencing machine) try and remove the Office Software Protection Service (does this still exists in Office 365 KMS??) so the appstack cannot update office licenses. It worked for us eventually.
And if you updated after December 2014, did you make sure to also update the Appstack template files? Lasts ones have had some better results with office.