If I try to put complex elements in my <li> elements for the ribbon tab, I sometimes see the following console error when I select the tab.
Uncaught TypeError: Cannot read property '_disabled' of undefined
A few weeks ago, another user noticed this in one of your examples (here, showing icons in the header).
Clicking on the tabs in this example yields this error in about a quarter of the clicks for me.
In my case, I had been trying to put a div in the </li><li> element and it was almost always happening (and subsequently not changing tabs).
(v3.8.2 referenced at time of test)</li>