can't boot into safe mode

Since upgrading to High Sierra, there are 2 things that don't work:

1. the system freezes when I use the Disk Utility app. (Note: I can run Disk Utility through the Recovery process). I have not seen anything that suggests that the Disk Utility app doesn't work. Should it? If it should, why doesn't mine work?

2. when trying to boot in Safe Mode, the progress meter gets to the end but does not go into safe mode.

Thank you.