Aren't 'sir' and 'professor' identical?
Both should be accepted. Report it.
Yes, اُسْباذ is for both [male] professor and sir. Just the same as when اُسْبازة is for both [female] professor and ma'am [which means madam].
This should also be accepted:
Are you a translator, professor?
(Check the pronunciation on أُسْتاذ.)