On Thu, Dec 21, 2017 at 17:16:03 -0600,
  Bruno Wolff III <bruno@wolff.to> wrote:
>
>Enforcing mode alone isn't enough as I tested that one one machine at 
>home and it didn't trigger the problem. I'll try another machine late 
>tonight.

I got the problem to occur on my i686 machine when booting in enforcing 
mode. This machine uses raid 1 vua mdraid which may or may not be a 
factor in this problem. The boot log has a trace at the end and might be 
helpful, so I'm attaching it here.