Like the scrolling problems mentioned here, cs-body.js seems to have some problems in IE11, even though it looks like you are using a relevant polyfill.
Pages using the mejs audio trigger this error message in IE:
Object doesn’t support property or method ‘includes’
and audio controls are not created, leaving that post type effectively unsupported.
See an example on my site (I’ve turned off CSS/JS concatenation/minification) [edit: back on now]: