I have around 8 crafting charatcers on my account. Only one has duplicate kits, I don't mean there are 4 in the series based upon ratings (150, 300, 500, 550), but I mean duplicates of the ratings for Infantry Supply Kits. In essence I have 2@150, 2@300, 2@500 and 2@550, which about as useful as a chocolate tea pot.
This effects just how many kits I can make in total (4), whereas other crafting chars all get 8 (2 sets of 4, different kits).
I can only assume that the other chars that can also make Infantry Supply Kits, that I'd taken other skills before the Infantry ones, whereas on the one char, I'd taken Infantry first and ended up full !!
Either way this is a repeatable bug, and if it never gets fixed, be warned to take Infantry Supply Kit skills last from your crafting trainer and not first.