I was in Trainer mode today and my system froze 2 times at the exact same spot on the Volcano Flat course (at the fork). Started system for third time and did Watopia course and did 2 laps, worked fine.
You are not the only one see this post:
https://support.zwift.com/hc/en-us/community/posts/115000225663-ZWIFT-Freezes-new-Volcano-Section-1-