There's a bug with NavBar creation that's been introduced in V16.1 that won't be patched in time for its release very shortly. We are working on a fix although I can't say when it will be ready to be released.
What is the bug? After creating a Navbar from a button (arrange > Create Navigation Bar) and previewing, some of the buttons will appear out of place than they should do.
To fix this, before going to Arrange > Create Navigation Bar, select the buttons > right-click > Web Properties > Image > select the option "One image for whole group", then create a NavBar out of them and it should appear normally.
If you have already created the NavBar in V16.1, simply ungroup it, change that option previously mentioned to all buttons and re-create which should fix it.
This won't affect any NavBars created before 16.1 or templates in the CC.