When the button is first tapped, the three buttons (Post, Upload, Cancel) lose focus and are greyed out. After a few seconds, the Post button remains yellow, the other two reappear, and I have to tap Post again...and often, one or two more additional times. This happens on our big board as well as our private test forum on the same server. On a friend's installation, just this morning, I had the same issue. I know our big board can often be busy and some actions might take an additional couple of seconds if we're really slammed. But my friend's forum is very low traffic (but I believe he is on a shared server).
Did not yet report this as a bug, but if others have seen it and it can be duplicated, perhaps it is a bug and should be moved there. At any rate, on our big board, it is one more issue they are likely complaining about.