Maybe making multiple premoves?
"Phantom" Moves not Seen?!?!?!

Yes, this just happened to me! I moved a pawn to block a queen check in a daily game and when I came back to the game a minute later, the queen check had apparently never happened! It had been a tight game, but the ensuing sequence resulted in the immediate loss of a knight and it only worsened beyond that.

Yes, this just happened to me! I moved a pawn to block a queen check in a daily game and when I came back to the game a minute later, the queen check had apparently never happened! It had been a tight game, but the ensuing sequence resulted in the immediate loss of a knight and it only worsened beyond that.
Do you have a link to the game?

Chess: KennyK vs drurodz - 359386063 - Chess.com
It happened on move 8. Instead of Be2 as the record shows, he had moved Qh5. Thus, I responded with g6 to block the queen check. I would not otherwise have done that with his dark square bishop threatening my rook.

Chess: KennyK vs drurodz - 359386063 - Chess.com
It happened on move 8. Instead of Be2 as the record shows, he had moved Qh5. Thus, I responded with g6 to block the queen check. I would not otherwise have done that with his dark square bishop threatening my rook.
I've never heard of something like that happening. I guess it's possible there was a browser cache issue that loaded the position in correctly.
So many times I am "missing" some phantom opponent's move....so I move and then something that didn't happen on the board is shown--usually with catastrophic results...
has anyone else had this happen???