Oh, I thought that was packing material...
And I was getting ready to say "It was only a matter of time..." but since it holds under load and under switching (yeah, I know, switching is a series arc) then I'd call it good.
By all means if anyone has trouble with AFCI's "nuissance" tripping, then please report here about it whether you've solved the problem or not... We all need to know as soon as possible, to help combat the inevitable.
Steve, (sparky) you've still had mostly good luck with 'em?