We keep seeing this over and over that there are multiple posts by the same person or responses to a post by the same person. I am running Windows 7, Windows 8 and Windows 10, and I have the same problem on all versions, so I know it isn't specific to one Windows platform.
I can also tell you that it is not something that happens every time, but it happens quite often and it happened again this morning.
As an example I was replying to a post with a scooter and when I typed out my reply and clicked on the POST button, nothing happened. I waited for over a minute to see if it would finally accept it and move to the next screen. Nothing happened. So I clicked on it again, and nothing. I bet when I go back and look, I have two posts and have to wait for a moderator to delete one of them.
The system also does this with New posts.