I was just at their factory last weekend for the Sig Fly-In. Yes there are lots of things that are out of stock. They have changed their website to reflect that the kits are sold out, which I believe are to prevent people from ordering them only to find out later that they are out of stock. They are working to fulfill orders but there are supply issues and just not enough people in my opinion. If you are wanting something in particular, you need to call and speak with someone and they will tell you whether they can ship that immediately or not, then you can decide if you want to place an order.
You have to realize that they sell worldwide, so say they manage to get 3000 Kadet Mark II' kits in stock. They will be gone instantly due to back orders, then the kit is "sold out" again. Everyone is just going to have to be patient with them. They will be back, but it is going to take time.