After signing borerus, is there any way to back out before a psak is issued?
During the diyun, the rav said something against …, and I question his validity as a moreh halacha. Had I known this about him, I never would have agreed to sign his borerus.
When you sign borerus, it is binding, and I don’t see any way that you can back out of it. This is the whole reason why we sign before doing borerus, in order to give validity, to what the Rav says.
As a side point, whatever the Rov’s views about… and he fact that he said something that hurt does affect the way you trust him, however it would be helpful for you to do whatever you can to enhance that trust. Here are some ideas. Whatever his views about … are, this is not going to change the fact that if he is qualified to answer correctly, what he paskens has validity. No different that going to a doctor, and he says his personal view about a certain topic, should not cause you to change doctors. When he gives you his medical diagnosis it is an objective answer, unrelated to his political views. It should not be any different with this.
Additionally, if he is a talmid chacham we surely have the obligation to be dan lekav zechus, that maybe there was a misunderstanding here, and he didn’t mean what he said in the way that it was understood.
Hashem should help you that you question should be answered correctly, so the emes will come out.