I joined, not on the basis that it was the truth, but on the basis that as a group of Christian people, this was the best group going at the time.
In my study (1991-92) I noticed things which I felt were wrong and I spoke to elders and my study conductress. The things I noticed were not deal breakers, just grey areas. I was told that if the GB had got anything wrong they would correct it. They were not like the Pope who claimed infallibility. They were not like higher critics who attacked/changed the message in the Bible. So I was lied to. It took some time for me to realise that I was being lied to and that GB would not change their 1914 doctrine as it was the base of their power.
Even down to the very end, before I called them out as standing in opposition to Jehovah's Witnesses, such as Daniel, Ezekiel and Jeremiah, I gave them the chance to correct matters but both GB and local elders were unwilling.