Daniel -- Good eye - you are exactly right! I noticed the problem with that hinge back when I created the multi-material remix (and fixed it in the remix). I didn't address it in the original model then because so many of us have printed the cube successfully even with the defect (thankfully there's a fair amount of clearance in the model to allow this). That said, it's been on my "to-do list" to correct it and I hope to do so soon. I'm a little behind because I'm moving, but I will get to it!
Thanks for posting!