We use the navigation when exporting with in5 and found that the wrong attribute is used there.
The following line can be found in the code (in5.viewer.js):
var $vwrap = $('<footer id="viewer-options-wrap" class="collapsed" aria-role="toolbar">');
However, the "aria-role" attribute does not exist. The correct attribute name is "role".(see here: https://www.w3.org/TR/html-aria/#allowed-descendants-of-aria-roles).
Thank you for a hopefully quick fix.
Thanks for bringing this to our attention. You're right. There are some references to aria-role that should simply be role. This will be updated in v3.8.9 in a few weeks.