Well this isn't to strange, since you as you say check to se if the position is valid that is, as I understand it, that no other piece is there.
I think that your problem is one of logic where each Tile is deciding if its blocked and moving which is wrong. Suggestions.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.