I appreciate the recognition.
There is a way to lock the moves, but it was too labor intense for me. Basically go thru all 96 tiles and make a list of all adjacent tiles marking them as above, below, to the left, to the right and have a recursive algorithm go thru it all to create a new list with all possible moves and lock all others. This would also make the AI play fair.
I approached it wrong in the planing phase. You only see the error in your way when you have to actually implement what you thought up. The diagonal moves really messed with my whole logic, because it makes a big difference for your final position whether a move to the top right is defined as moving up and then right or moving right and then up.