Time to get Astaro Support involved. Just out of curiosity, you might look at the High Availability log. I've seen a situation where the MTUs of the sync interface became mismatched in an Up2Date, but that needs to be fixed at the command line.
Cheers - Bob
Sophos UTM Community Moderator Sophos Certified Architect - UTM Sophos Certified Engineer - XG Gold Solution Partner since 2005