This idea applies to the browser interface of Canvas
If a section filter is applied in the markbook this filter is also applied to the speed grader.
This has caused confusion for many of my teachers, as when they open an assignment in the speed grader the student list only has 'Test Student'. This is caused by the section filter in the markbook removing the students from other sections, even if those section are appleid to the assignment
If there are multiple teachers in the course, one teacher can inadvertantly hide anouther teacher's students! There are multiple paths to the speed grader, its easy to not use the markbook to access the speed grader and not realise there is a filter in place. This can be solved by showing any applied section filters in the speedgrader.
There may be other solutions to this issue.
If a course has assignements assigned to specific sections, why is the speed grader being filtered at all, when the expectation is that the students doing that assignment are just visible? Choosing the assignment is the filter that should be applied.