It is entirely likely that the BOTs have been holding Cudeco back hoping to shake out some of the weak long positions. (It doesn't appear to have work over the last five trading sessions.) These guys are probably building a position, and are happy to sacrifice a few pawns to improve their entry price.
I think that it is smart trading. I can't see what is unfair about it.
As a long term holder, you should sit back and watch the entertainment, confident in the knowledge that some rather smart players with deep pockets share your view that CDU is a good bet.