This might be a bug within Bootstrap itself, but I\'m still interested to see if anyone can come up with a fix or at least some help.
To jump straight to the issue,
The best solution we came up with was to hide the affixed column and show the same content elsewhere. Instead of falsely re-ordering the columns with pushes and pulls.
<section class="visible-xs">
NORMALLY AFFIXED CONTENT
</section>
<section class="col-sm-8">
MAIN
</section>
<section class="col-sm-4 hidden-xs">
<div id="affix-menu" data-spy="affix" >AFFIXED CONTENT</div>
</section>
Cannot comment yet so this is additional reference on the problem not necessarily an answer.
mdo says its an issue on github https://github.com/twbs/bootstrap/issues/12126 but then fat closed it saying "...to get around this you'd just have to make sure that you are styling the classes applied appropriately."