H. G. Muller wrote on Sun, Feb 6, 2022 09:12 PM UTC:
I tried to debug it some time ago, and the error message was provoked by the first halfmove of the game being applied to the position resembling the one that occurs after all moves have already been applied once. So the question is: why would Game Courier try to apply the set of moves twice? And, as I said, it also appears to execute the Pre-Game code twice. (But not fully, otherwise the first loading of the game would be fully erased, and undetectable.) I had the impression it was due to the previous move being a check, but this could be a coincidence.
I tried to debug it some time ago, and the error message was provoked by the first halfmove of the game being applied to the position resembling the one that occurs after all moves have already been applied once. So the question is: why would Game Courier try to apply the set of moves twice? And, as I said, it also appears to execute the Pre-Game code twice. (But not fully, otherwise the first loading of the game would be fully erased, and undetectable.) I had the impression it was due to the previous move being a check, but this could be a coincidence.