I remove all the bdr packages and reinstall it and setup again the BDR cluster, still facing the same issue on 3rd node.
At this point I'd really need to see the steps taken, in detail, to get to that point from a clean initial state.
If I had to guess right now I'd say that the host pg3 isn't actually the node node3 that you are connected to when you're joining the node, i.e. the error message is correctly telling you that you've given the wrong external DSN.