Why does jQuery not work in iPhone6 but does on iPhone 6S?

Question

When I run:

$(document).ready(function($) {
    $("#nav_lat").slicknav({ prependTo: "#mobile_menu" });
});

on a iPhone 6S or iPhone 6 it works. But when I run:

$(document).ready(function() {
    $("#nav_lat").slicknav({ prependTo: "#mobile_menu" });
});

it works on the iPhone 6S BUT NOT the iPhone 6.

Both phones are using iOS 9.2.1 and there are no other changes to the code. What would cause a $ conflict in one but not the other?

Tested this on two Iphone 6S and three Iphone 6. By not working I mean the hamburger doesn't appear. Interestingly, if I use:

 jQuery(document).ready(function($) {
    jQuery("#nav_lat").slicknav({ prependTo: "#mobile_menu" });
});

it doesn't work in the Iphone 6