i think it happens in congregations a awful lot. So many bros and sisters consume too much alcohol but they seem to get away with it for years.
The problem isn't really the alcohol, it's more of: What you do under the influence. For old timers, it's easy to get away with it. They just have to say that they mixed two medicines together and it had side effect. I've seen it happen a few times.
But if weird stuff happen too often, they will get called out for it. In the case of AM3, he literally seemed under the influence of alcohol during public speeches!!! So, it probably got really bad, like, out of control bad, to the point the other members of the group had enough.
By the way, the rumors about an alcohol problem isn't just in the xJW community. I know some folks inside that heard the same thing without me saying anything.