Remember that the GB consider themselves to be the conduit between Jehovah and humanity. God guides the GB through holy spirit, and the GB then brings "meat in due season" to the faithful. This is also the way that god provides "new light" to Christians-- through his connection with the GB.
For the rank-and-file, this means that the GB's interpretation is the valid one, even if it may not appear to be consistent. And sure, they occasionally remind us that they are fallible men who get things wrong. But Jehovah can only work with what is available, apparently. So, even if they got it wrong, you have to believe it as if it is true. Eventually, they'll get it right. Maybe.