I read that B13's are known for door sagging, but my B14 does. When I open the passenger door, it 'sags' roughly 1/4-1/2". Is this an easy fix, or a design flaw?

easy fix just reallign the door and tighten it up

it could be the hinges, like on the B13 the little plastic part in the hinge breaks and the door sags

Check the lower hinge for wear. With the door open about 45 degrees, lift up on it. I bet you can wiggle the door up and down about as much as it sags when you open it. You should be able to see the play in the lower hinge where it is worn when you do that.