Hi, and welcome to the User BB!
I tried this behind a UTM 9.206-35 with Web Filtering in AD-SSO Standard scanning HTTPS and had no problem. Does #1 in Rulz give you any clues?
Cheers - Bob
Owner: Emmanuel Technology Consulting
Former Sophos SG(Astaro) advocate/researcher/Silver Partner
PfSense w/Suricata, ntopng,
Other addons to follow
all works here..traceroutes look fine. If this issue persists do a trace to them and see where the traffic dies.