Plagiarism checks: "Not enough valid submissions"

[tobiasjungmann]

Describe the bug

The plagiarism detection works without any problems for most of the exercises of the course GBS. Only two of our exercises result in the error message "Not enough valid submissions! (found 0 valid submissions)" after downloading nearly 300 submissions. This error occurs for different thresholds and reruns. Are we missing something while performing the plagiarism detection, or is something going wrong internally?

To Reproduce

1. Go to an exercise with the problem: e.g. https://artemis.ase.in.tum.de/course-management/278/programming-exercises/11597/plagiarism
2. Trigger the plagiarism detection (after lowering the threshold).
3. After downloading submissions the error message occurs.

Expected behavior

Receive the overview of potential cases of plagiarism as in all other exercises

Screenshots

No response

Which version of Artemis are you seeing the problem on?

Version 6.9.0

What browsers are you seeing the problem on?

Safari, Firefox

Additional context

No response

Relevant log output

The request "https://artemis.ase.in.tum.de/api/programming-exercises/11597/check-plagiarism?similarityThreshold=40&minimumScore=0&minimumSize=0" results in an error 400.

[krusche]

which thresholds did you use? it might be the case that submissions are filtered out and then no submissions are left

[tobiasjungmann]

We've tried it with 5, 30, 50, 70 and 90.