Errors of rabbinic authority are potentially harmful

from my sefer Daas Torah - translation copyrighted

Derashos HaRan (#11): … Since we believe that all which the Torah prohibits is inherently harmful and creates a harmful impact on our souls – even though we don’t know the reason. According to this accepted view, even if all the sages mistakenly believed that something that was impure was actually pure – this agreement doesn’t change anything and it still remains harmful to us and its actual harmful nature continues despite the mistaken understanding of the sages that it is pure. It is equivalent to the agreement of doctors that a medicine has no effect when it is in fact a strong drug. There is no question that there is absolutely no significant change in the nature of the medicine that results from the mistaken agreement of the doctors. In the same way if the Torah prohibits something because it is harmful, the agreement of sages that it is permitted doesn’t change its intrinsic nature – except by some miracle. … [Thus we see that when the Sanhedrin errs and causes people to violate that which the Torah prohibited – they are causing harm.] However it is inconceivable that a person should be harmed by following the ruling of the Sanhedrin even if he eats something which is prohibited because they said it is permitted. The answer is that the soul greatly benefits when a person listens to the Sages since it is the action most beloved by G d… This benefit removes the harm which would naturally result to the soul because of the eating something prohibited. Something similar happens physically when a person eats something which is harmful. If he eats it with the understanding that this food is good for him – his thoughts act on the food and remove the harmful effects – unless the harm is  very strong. It is the same thing when a person follows the commands of the Sanhedrin and perceives something that is objectively prohibited as being permitted. When he follows their directives, that obedience itself will remove all harm that he would normally be subject to because of the natural consequences of eating something which is harmful. That is why the Torah commanded to follow the directives of the Sanhedrin and not deviate either right or left [whether they are correct or not].