This is definitely an IE issue. From the JQuery 1.9 upgrade guide:
Unfortunately, all versions of Internet Explorer (6 through 10) fire focus events asynchronously. When you .trigger("focus") in IE, jQuery won't "see" the async focus event which will occur later, so it fires one of its own to ensure that a focus event always occurs as described above. This causes two calls to the event handler. To avoid this double-call--but risk that the event handler is not called at all--use the DOM focus method directly, e.g., $("selector").get(0).focus().
I used $('input').get(0).focus()
and it was not very consistent on the loading of the page. If I move the code to a button, then I consistently got the focusin
event firing.