I have heard some breeders comment that they some bags of megazorb did not agree with their hamsters mainly because they had quite a lot of black gritty ash in them. This is formed during the processing and it can make the feet sore and also stain the coat.
We had a bag that smelled terrible once - like sick
I think it must have been stored damp and this had caused the problem so I expect there might have been fungus or bacteria in in to cause that which could have caused a reaction. We never used it.