Case: The plaintiff (=pl) sold the defendant (=def) a commercial shipment of dates. After the sale, def asked pl how to store them. The dates became wormy before def was able to sell them, and he refuses to pay pl for them.

Ruling: Ability to void a sale: One can void a sale if the root problem existed in a hidden form prior to the sale, e.g. an animal was treif (Chulin 50b). In that case, if we do not know if the treifa occurred before or after the sale, the one who wants to extract money must bring proof (ibid.). The Shulchan Aruch (CM 232:11) rules that even if the buyer did not yet pay, he must do so unless he brings proof the blemish had already existed. Since the blemish was found in the buyer’s auspices, this is where we attribute it to have arisen. On the other hand, the Shulchan Aruch (ibid.:16), as the S’ma (232:34) understands him, says that if one bought cheese, which turned out after three days to be spoiled, we do not make him pay if he did not already do so. The distinction is that it is common for cheese to be predisposed to spoilage (ibid.). We cannot apply the latter logic to our case because the distinction is not clearly accepted and because in this case, there is no claim that the worming already began.
Responsibility for bad advice: Although pl and def disagree as to what advice pl gave, an expert said that even the advice pl claimed to give was faulty. The gemara (Bava Kama 99b) says that a non-expert who gives bad advice regarding accepting coins that another relies upon is obligated to pay. Although pl is not an expert, it is, for two reasons, difficult to obligate him. First, the semi-direct damage of giving bad advice obligates payment (as garmi) when the damage is basically immediate and certain. In this case, an expert determined that had def sold the dates within a reasonable amount of time, they probably would not have developed worms despite the advice.
Furthermore, the gemara (ibid. 100a) says that only if the advice’s recipient told its source that he was going to rely upon it does he pay. Although there is a dispute how explicit one has to be (see Shulchan Aruch, CM 306:6), in our case it is was clear enough that def was relying upon pl. However, def did not prove that he actually followed pl’s instructions. If def anyway did what he wanted, the damage would have occurred even if pl would have given correct instructions. Pl may even have stored the dates in a worse manner than pl instructed, thereby causing the damage.
Therefore, according to the strict law def must pay the full amount. However, since pl signed the arbitration agreement that allows compromise to be included, beit din gave some weight to the element of indirect damage that pl apparently caused and reduced the sum that def had to pay.