Other mistake: When the old well needs filling in, for safety reasons, Ryan is breaking up bricks. If you are filling up a well, first, you'd need lots of bricks and stones, heaps more than Ryan's small pile, and, two, why does Ryan have to break up the bricks? They're going into the well - it doesn't matter if they are big or small.
Other mistake: When Rosemary comes back from seeing her old college professor, she comes in from the garden, but Julia's place - this is where Rosemary and Laura are staying - is on the first floor; there's no access to her place from the garden. Rosemary should have gone to the front door, on the street.
Other mistake: When Malcolm is found dead with an arrow in his chest, the arrow is pointing down at an angle, which means it came from someone high up, but, later, we find out it came from someone of around the same height and standing on the ground, not high up on a ladder, or on a rooftop, which it should be, to get that angle.