A lot of these things could be a problem. Bought a new Cameo and 1 month later had smell. Dealer checked everything, and finally opened up black tank. We had a pyramid. Problem was using a treatment that had froze over the winter killing all the bacteria. Dealer used Digest It and overnight liquified the pyramid. Last year had problem again. Read label on Digest It and says do not allow it to freeze. Bought a new bottle and got rid of problem. This stuff works. We do use more water then whatdirections say. Outherwise follow instructions.