I'm sorry about comment about the heads being on backwards. My wife says I have the worst sense of humor. I guess it really was a BAD joke.
So no the heads cannot be on backwards.It's impossible.
One thing nm9 may have missed is a cracked shaft at that hole, which is what I was thinking in a previous post. But it's far more likely to be the spacer or the bolt.
Also, just because the bolt reaches it's torque spec , does not automatically mean it's correctly installed.If the bolt is too long for instance, it could bottom in the hole,reach torque spec, but not be tight. Or if there's something in the bottom of the hole. or the bolt shoulder ends up in the wrong place,or if threads are bad,etc.