sum of account balances before and after instruction do not match

Question

If ctx.accounts.game_match.won is true, I don't get any errors, but if I go to the else block, I get the error mentioned in the title. But why?

   if ctx.accounts.game_match.won {
            msg!("you won!");

            ctx.accounts.game.win_count += 1;
            ctx.accounts.game_match.won_amount = bet_amount * ctx.accounts.game.multiplier as u64;

            let transfer_amount = ctx.accounts.game_match.won_amount - bet_amount;

            msg!("transfer_amount: {}", transfer_amount);

            **ctx
                .accounts
                .game
                .to_account_info()
                .try_borrow_mut_lamports()? -= transfer_amount;

            **ctx
                .accounts
                .player
                .to_account_info()
                .try_borrow_mut_lamports()? += transfer_amount;
        } else {
            msg!("you lost :(");
            msg!("bet_amount: {}", bet_amount);

            ctx.accounts.game.lose_count += 1;

            **ctx
                .accounts
                .game
                .to_account_info()
                .try_borrow_mut_lamports()? += bet_amount;

            **ctx
                .accounts
                .player
                .to_account_info()
                .try_borrow_mut_lamports()? -= bet_amount;
        }

Answer 1

Make sure that player has at least bet_amount, otherwise you'll be doing an overflowing subtraction, which means that you could be setting player's lamports to a huge number close to u64::MAX!

Also, be sure that player is owned by your program so that it can properly decrement its lamports.

Answer 2

Shot in the dark, but... maybe decrement "player" first and then increment "game"? That is a big difference I see between your first and second scenario.