Using 16.1.3-amd64 release, using over 10 Hosts (Firewall > Aliases) the Save and Cancel buttons disappear behind the 'OPNsense (c) 2014-2016 Deciso B.V.' bar.
But the main culprit is the Save button doesn't work (even with less then 10 Hosts), nothing happens. Cancel button works. Tested on Chrome 48, Firefox 44 en Internet Edge.
I think you're experiencing this issue: https://github.com/opnsense/core/issues/785 (https://github.com/opnsense/core/issues/785)
Can you test if these instructions solve your issue as well? I'm not sure if the other user had the save issue as well.
Yes, it works, thx!
Thank you for your feedback!