Hi
It was a long time ago now so can't remember fully. But I think it was related to the fact the affected users had a Profile path set in their Active Directory account and when they were going into the office and connecting to the corporate network directly on their laptops. This was changing something but can't remember exactly what. When we removed the profile path it seemed to fix the problem.
I think FSLOGIX uses the local_user.name when users log onto Citrix so I think this was conflicting with the profile path setting.