I get what’s it’s saying. It’s receiving a move from the wrong player (me) apparently but I can’t fathom why. I’m just using PC, windows 10 Opera with no shenanigans. 
ps. It was a bugger to catch this shot. It only appears for a second and very hard to guess when.
I’ve never seen that before 
I would guess it’s not meant to be visually displayed… but even given that hypothesis, I’m stumped as to why it randomly is
I would guess that is has something to do with my poor connection. As a coder you are likely to have a better one and therefor never encounter it. I get it a fair bit which is the only reason I was able to eventually ‘catch’ it and actually read it.
I like to collect “Orange on black unicorns”. lol
Got it twice right now.
Basically when I move I place stone → submit move → stone disappears → after a few seconds stone reappears (I guess when server confirms it received it or something).
And I guess because of move appearing-disappearing if you time it right it might look like wrong side is trying to move.
Additionally, when I receive opponent’s move sound and “your turn” indicators work right away, but it takes seconds for the board to render it. Which is weird because if sound works then my browser received the move just fine and it’s not entirely connection problem.
Today OGS was quite close to unusable for me in terms of playing.
Additionally, may I take the liberty to change the topic name to something more searchable.
Edit: yeah, probably board is trying to resubmit the move when it already reached the server. I tried to play E5 but it says last move is already E5.
FYI: possible to simulate slow connections if you (or others) want to have an easier time reproducing (Simulate Slow Internet Connection With Chrome Developer Tools - Andreas Wik)