As far as the spindle hitting the spring I'm going to say there's not much you can do about it. Unless something was installed wrong?
I would contact RCX on that one.
The popping sound when you turn makes me thing you have something installed wrong.... It shouldn't be doing that. I would start with checking your CV shafts making sure they're in correctly and then check the ball joints and tie rod ends.
As far as the shutter goes, how does the rear pinion angle look? That's what would likely cause the shutter. Post a picture of that up so we can take a look. The front one looks very similar to how mine was.