I'd also lean towards an artifact of the high level winds, noticeable after the aircraft's passage. I suppose it could also have been "finger trouble" ("Hey, what's it doing in heading mode?"), but that seems less probable at that stage of the flight.

From the article you linked to - I particularly liked:

Somebody said a UFO had been spotted recently in the area and the pilot had tried to avoid it

She did say that she liked the sound of that, and not that she believed it for one moment. More worrying was her assertion about there being no wind. True at ground level, perhaps.

A shame the reality is always so dull.