In some of the posts above there does seem to be a suggestion that this blatant sabotage for financial gain was somehow caused by management's failure to manage.
I would suggest it is not about that at all.
While there are many hard working, diligent cabin crew there is also a small minority intent on harming BA in "weird and wondrous" ways.
It's good to see it's easy to frustrate their childish antics. But it shouldn't have to be that way.
BASSA et al must take responsibility for such "guerilla" activity, and BA must take a harsh line with the perpetrators to ensure they are performance managed out of the business.
BA Management has neutralised the threat to passengers, but the threat to other BA employees, shareholders and pensioners remains; it will remain until BASSA's present leadership is marginalised and voted out.
That can only come from within the ranks of current BA cabin crew.