I am about to buy a used 1299s and have been reading various threads on the forum. What have been the main issues with the bike.
Screens cracking/not working, water pumps, quickshifters, and a couple of recalls. Nothing in enough numbers to say it is likely to happen to the bike you buy....
Mainly electrical for me. One fault a month (two this month) in a year of ownership and I don't even have electronic suspension (base). For balance I use my 1299 everyday in all weather and my wife and dealer are convinced I have some sort of inbuilt electromagnetic pulse device. Great bike just make sure you have a warranty on it, you live close to a dealer and they are happy to lend you a demo bike should yours require surgery.