“The Governing Body is neither inspired nor infallible. Therefore, it can err in doctrinal matters or in organizational direction... Of course, Jesus did not tell us that his faithful slave would produce perfect spiritual food."
That is a quote from The Watchtower of February 2017 study edition pg. 26.
One of the illustrations I learned as a JW involved a glass of refreshing drinking water that had one drop of a virtually undetectable poison in it. It was enough to kill you if you took a sip, though you could never tell by just looking at the glass or even drinking out of it until it was too late. They used this to illustrate other religions, ironically. Their thinking was that even if the teaching of a religion was 99% good, it was the 1% that would kill you. In contrast to the 100% purity of the accurate teachings of the GB/FDS. Except in the above quote they openly admit that they were neither accurate or pure themselves!