After switching to the Authentic theme, the Network->Linux Firewall page is never displayed. The progress bar across the top progress to the end, but nothing is displayed. I switched back to the original theme and it works fine.
Granted the network firewall list is somewhat large, with several hundred lines and might be contributing to the issue.
The server config:
Browser - Chrome Version 51.0.2704.84 (64-bit)
While I love the new layout of the Authentic Theme, it is slower than the original "Virtualmin Framed Theme". Which in itself would not be a deal breaker, but the inability to add/view/edit the network firewall is.