For example, if you go to https://chess.academy/test/ and click on the forward arrow one time so that the first move is played, it looks like the c-pawn moves from c1 or even outside the board.

It's only on the small boards; it doesn't happen on the bigger boards. I don't know if this is a bug within the plugin or if maybe my theme is causing the issue. I have a feeling it's my theme but I want to be sure. Perhaps someone else could try to reproduce it on his website?

Thank you very much.

Edit: I'm using Chrome but I also tested in Firefox and I get the same result: the pieces do not animate from their original squares on smaller boards (when I resize the window down to what a smartphone would be, for example).