During a recent project, an apparent software bug was encountered. The issue occurred with a Cisco 3850 that was 16.6 variant, and again on 16.5 after rolling back to the original version and required a significant amount of time to resolve. The project utilized a 3850 stack in a collapsed core type of deployment where it was being used as core and distribution. The 3850 was connected by 10GB single mode fiber to 11 different stacks, and then used copper interfaces to MPLS