Once or twice when I've made a move recently, my browser hangs in waiting mode for much longer than usual (I guess maybe 10 seconds), then reverts to my list of games. I find that my move has not been accepted by the system, it is still my turn. I go into the board and make the same move again and all is well.
This is not a big issue, and it may be the fault of my browser I don't know. (I use Firefox, Windows 10 and a Dell Desktop computer.) Just thought you might like to know about it in case it is a bug.
If you have a log, it happened to me at about 19:48 on 14 Oct 2018.
That's been happening to me quite a bit recently. (W7 desktop, Android7 tablet). I've been blaming the Pacific underwater internet connection because my Australian-located servers don't seem to suffer from it. But now that I think about it, most of my interaction with the US is on this site.