I implemented a negamax with alpha beta and aspiration windows. Now, it also has iterative deepening. When I let the engine run for 15 seconds in the below position, it finds a move at depth 2 with very good value (135/ d8-d7). But when it goes one depth deeper, the movie is bad because it loses the queen (980). Looking at the best move at the deepest depth, when it fully searches, I get f7-f6 with an evaluation of 200 and it is a way better move.
Do I just throw away the best move of a previously searched depth, and only look at the deepest fully searched depth? My brain somehow can't find the solution.
[FEN "rnbqkbnr/5ppp/4p3/2PN2B1/1P2P3/p4N2/P1P1BPPP/1R1QK2R b Kkq - 0 1"]