Leveling compound: Bags are hard

Hello,

I ordered 7 bags of leveling compound from Probau and 6 of the bags are completely hard, the other one soft, like a bag of flour. The seller said this is quite normal, but now I am wondering, before I make the time to pour the floor, if the hard bags are really still usable - have you already had experience with this phenomenon?
Thank you very much for your advice.

I wouldn't have believed that from the seller.

Hmm, opened one and tried to loosen it with the trowel?