iMac hangs trying to restart or shutdown 10.13.3

I'm having an issue with my iMac where it hangs during shutdown. It gets to a black screen with just the cursor showing. I am able to login from another computer via SSH and see that it's doing nothing (according to CPU usage). The system.log didn't show anything of interest either. I discovered this when trying to update the supplemental update just released. It won't install because I have to do a hard shutdown (either holding the power button or issuing sudo shutdown -r now via ssh).

I read that booting into safe mode can get you past this but every time I try it hangs before completing boot-up. I've tried disabling all startup items and launch items but hasn't helped. I've tried resetting SMC and PRAM and Disk First Aid. Single user mode still hangs on shutdown.

Obviously I could try reinstalling but I want to avoid that if possible. Any other suggestions?