Devarim 17:6 says that the testimony of two or three witnesses should be used to determine the death penalty for someone who was found to have bowed to idolatry. Rash"I implies that all the witnesses have to concur and form a unified testimony - whether that means 2 or 3 people. I.e., if you have 2 that say one thing and the 3rd says the opposite, the entire group is invalidated.
I'm curious if there are exceptions to this unified concurrence. For example, I recall reading that regarding the witnesses that come to Jerusalem for the purpose of Kiddush hachodesh (new moon), two witnesses need to concur. The witnesses are questioned, and if a group of two appear and the two give different opinions, Sanhedrin waits for an outsider to appear and concur with one of the others so that eventually they will have two concurring witnesses.
Can this same scenario apply to criminal or civil cases, in general? Or is Rashi's explanation regarding unity applicable only to this specific scenario of serving idolatry?