After importing the gradebook as .csv-file back to the course the following problem happens:

• if a teacher does the import, then always the main administrator appears in the feedback information 'graded by' in an assignment.

• Then the outgoing mail to the student was also sent from the main administrator (and not from the importing teacher in the course as sender)
• Also - after the import - there is still the information 'Not graded' at the assingment:
  

If the gradbook is directly exported and imported via the assignment then the teacher (and not the main administrator) appears. But the 'grading status' at the assignment is stll on 'Not graded'.

I tested this on two different Moodle 3.4 and 3.5 standard-systems.

A similar tracker entrance I found here:https://tracker.moodle.org/browse/MDL-60685