I believe this bug is related to the premove bug with the Xiangqi Knight move (also relevant for the Dragon Bishop). You cannot premove a move in a blocked direction with a Xiangqi Knight, even if that direction will be unblocked on the next move.
The jumping spell simply does not work in conjunction with these pieces at all. Xiangqi Knight moves cannot jump over a piece that has the jump spell casted on it.
unrelated to the post. The jumping spell doesn't work for Xiangqi Knight moves. Just a coincidence that premoves also don't work for Xiangqi Knight moves.
I believe this bug is related to the premove bug with the Xiangqi Knight move (also relevant for the Dragon Bishop). You cannot premove a move in a blocked direction with a Xiangqi Knight, even if that direction will be unblocked on the next move.
The jumping spell simply does not work in conjunction with these pieces at all. Xiangqi Knight moves cannot jump over a piece that has the jump spell casted on it.