My advice, as always is to buy a K13 as opposed to a K12.
The 12 had certain, how shall I say, foibles which will most definitely mar your enjoyment if and when they arise. The 13 by its nature (it was a development of the 12 and therefore improved in many ways) has fewer 'foibles'.
The 13 also its little ways and isn't perfect but it is a far better bike than the 12 and its foibles won't break your bank but they will cost time and/or money. Chris has spent a lot of time and some money getting his sorted and it will probably go into the grave with him (not too soon we hope).
If you 'must' have a 12 then get a late one, the later the better.. But, the prices of the K are barely much different between a late 12 and an early 13 so there is no excuse for buying a '12.
If you go here...
https://eurokclub.bike/index.php?topic=3984.0...you will find most things you need to know.
Also, if you are a keen rider (as opposed to a plodder) then the chassis on the 13 is far superior to the 12.
Good luck and keep us posted.
Brian (who rode David's K13S, fully loaded for touring, for an afternoon in Spain when we did a swapsy. He had offered the ride to another, non-K bike rider over dinner the previous evening as he couldn't understand the attraction of all the K's on the trip. David was 'kind' enough to let me take up the offer and no, I haven't forgiven him. When we arrived at our hotel for the night our comments about the bike we had just been riding couldn't have been more different. You can read my subjective comparison here...
https://eurokclub.bike/index.php?topic=578.30