The "Unknown Name" is set during the Offerings XML import when an instructor is referenced by their external ID, but no matching instructor exists in the class's controlling department, and no name is provided in the XML (the fname and lname attributes of the instructor element). A new instructor record is created with the provided external ID and the name "Unknown Name". You can check your Instructors page; you will find them there.
Not sure about the prohibited preferences. Are there any preferences set on those instructors? Also, please confirm that the assigned time pattern matches the minutes per week specified in the scheduling subpart (minutes per meeting times number of meetings per week must match the minutes per week on the subpart), and that the date pattern EveryWeek has some days enabled (marked yellow on the Add/Edit Date Pattern page) during the days used in the time pattern.
Typically, you need to set up departments, subject areas (require departments), rooms (require departments), instructors (require departments), courses and classes (require subject areas), instructor assignments (require instructors and classes, or done with the courses and classes in the same step), and student course demands or curricula (require courses), in roughly this order.
Please note that we have a lot of documentation available, including the
administration and
course timetabling data entry manuals, which can be very helpful even if you are set on using the XML interfaces rather than the user interface.
Best regards,
Tomas Muller