Re: UPDATE: Microsoft Exchange 2016 CU5 - Breaks SMBR

 By the time you posted yesterday, the pre-release was already the official release.

SMBR 7.2.1 should be compatible through Exchange 2016 CU5.  Exchange 2016 CU6 included changes that caused issues similar to what you're describing.

I suggest opening a ticket to get the patch for CU6 to see if that resolves the situation.