G'day fellas, the pop and click under braking is most likely the steering head bearings. There is a nut under the top triple clamp (undo the top two fork retaining bolts on each fork leg, then remove the nut on top of the triple clamp....remove the top triple clamp and you will see it...it has holes in the sides for a crescent wrench, like you would use to adjust preload on a shock...the one in the tool kit does not fit!?!). Mine has loosened up 5 times in the last 8,000km. First 3 times I took it to the dealer to get them to sort it...next time I did it myself without removing the top triple clamp...just loosened everything up and tightened it down. Last time I removed everything and put some loctite on the retaining nut....hopefully that has fixed it!
There have been some bad front discs around as well. Some with too much fore and aft movement in the floating pins, which could cause the popping feeling, and mine warped after a couple of track days which created a front end shimmy under braking (replaced under warranty). The discs issue seems fairly isolated, but the loosening headstock nut is very common it seems, and ultimately a very simple fix...astounding KTM have not caught on yet!