Not 100% sure on the root cause, but I suspect it has to do with the way that the WebComponents polyfill works when encountering a previously cached <link> tag.
Setting the display style of the button icons explicitly to block fixes the bugs as reported.
Not 100% sure on the root cause, but I suspect it has to do with the way that the WebComponents polyfill works when encountering a previously cached
<link>tag.Setting the
displaystyle of the button icons explicitly toblockfixes the bugs as reported.