In IE 11.0 tabbing through Selectize fields is broken, try this example, focus the first field and then press tab. It should now focus the second selectize (note that there are even added tabindex properties).

The reason seems to be the bugfix for "IE11 bug: element still marked as active" in onBlur:

(dest || document.body).focus();

This causes the document's body to be focused. Removing this line resolves the issue (see this fiddle), but I am not aware about the reason why this line has been added (and what issue it is trying to fix).