Well, online some people will say things sarcastically or humorously too, to make a joke. I wouldn't call it a lie, but if somebody didn't understand the context, or the person making the post, they might see it the wrong way.
There's also people who post what they've heard. They may be faithfully presenting it, as it was heard, but the information may not have been accurate to begin with.
And also, there's our own faulty memories. As time goes by, I might remember only parts of an event and try to tell it and tell you this or that happened. But that's me reanalyzing things based on what I remember. Then I remember some more details and realize that's not why things happened that way at all. I wasn't deliberately lying, I just wasn't remembering everything.
And there's also the, shall we say, mentally challenged? JW door-to-door reaches all kinds of people. Sometimes those people are insane and get duped into being a JW or become one because somebody's willing to pay attention to them. Some of those are ex-JWs now. With their mental state, some of the things they say and remember aren't accurate at all.
And yes, there are liars. If it sounds too fantastical, it probably is.
But I believe a lot of the people on this board and I'd say that lying is rare.