I upgraded to 2017 last night from 11.4.3. Let it sit overnight and started the Update 1 this morning. I haven't tracked the exact time, but it's been stuck at 99% for several hours.

Is that normal?

ZCC seems to be fine, and I'm doing System Updates on about 100 machines right now.

Windows Server 2012R2
MS SQL 2014 on Server 2012R2