I was looking at the Thaicom 8 falcon 9 launch and landing, trying to get a bit more info about the trajectory the first stage takes. The camera is however damaged and we miss most of the atmospheric footage.
It seems however that the camera was damaged because a grid fin on the rocket was lit on fire by the monopropellant. You can see the event in this video (It'll start 07:18 which is T+00:06:53).
I don't know which RCS fuel they use but I'd imagine it coming out pretty hot and being able to light some materials on fire. It seems like the rocket is a bit sideways to the air flow, which brings the smut from the fire straight to the camera lens. Does anybody know what the grid fins are made of? The paint on them might only be the flammable part too.
And, as a side note the landing seems really badly filmed, I'd imagine the would have had more cameras on the rocket and the barge, not only one which doesn't catch the landing and then freezes a few seconds after completely (they just show the last image I think there. Of course the rocket might have damaged their antennas but seems quite easy to shield them from a nominal landing)