I encountered this bug when upgrading from 7.1.5.N1.1 to 7.3.3.N1.1 on a Nexxus 5548. It was a very serious issue that took down everything I had on those switches, and the 7.3.3.N1.1 is the recommended version to upgrade to. I believe they need to rethink that being the commended version until they can get this bug resolved.