After upgrading from 8.1 Update 3 to latest 9.0 Update 1 a lot of icons are missing in the Experience Editor, but not all.
For example on the PRESENTATION tab only the Preview and Normal icons are showing up as you can see. The default Save/Search/New Component (top left) and the ribbon fold up/down icon (top right) are also missing.
I've tried to disable most of our custom code and tried with a clean installation (webroot only, not databases). I've also cleared my cached etc. but without any luck.
There are no failed requests being made (Chrome developer tools).
The buttons with missing icons just have a
<div> with a class indicating some sort of sprite.
<div title="Edit the current page." class="sprite-speak-ribbon-clean-ee edit_24"> </div>
The functioning icons have an
<img alt="Open Browser as normal" src="/temp/iconcache/office/24x24/eye.png">
Does anyone have an idea about what is going on or where to dig deeper?