Correct answer and feedback may disappear after manual regrading in deferred feedback attempts

[cmassoglia]

Description of bug / unexpected behavior

When a qtype_formulas question is used in a quiz with deferredfeedback, the correct answer / feedback block may stop being displayed after the question is manually regraded from the attempt review page.

The issue is not data loss. The model answers and feedback texts still remain stored in the database, but they are no longer rendered in the review page after manual regrading adds later grading-only steps.

Expected behavior

After manual regrading, the review page should continue to display the correct answer and feedback consistently, as long as:

• the attempt is finished
• the response data still exists
• the quiz review settings allow showing the right answer / feedback

How to reproduce the issue

1. Create a quiz containing a qtype_formulas question with visible right answer / feedback in review.
2. Configure the quiz to use deferredfeedback.
3. Attempt the quiz as a student and submit/finish the attempt.
4. Open the finished attempt review as a teacher.
5. Manually regrade the question from the review page.
6. Open the attempt review again.
7. Notice that the correct answer / feedback block is no longer displayed.

Moodle XML export

A minimal sample question can be provided if needed.
In our case, the issue was reproduced with a multi-part formulas question whose model answers were stored normally in qtype_formulas_answers.answer.

Error message

No explicit error message is shown.
The problem is that the correct answer / feedback block disappears from the review page after manual regrading.

Screenshots

Before manual regrading: the review page shows the correct answer / feedback normally.

After manual regrading: the same review page no longer shows that block, even though the data still exists in the database.

Environment

System Details

• Moodle version: 4.5.12
• Plugin version: 2026051800
• PHP version: 8.3.31
• Browser: Chromium: 149.0.7827.196

Additional comments

We inspected the database and confirmed that the issue is not caused by missing data:

• The question still had combined feedback stored in qtype_formulas_options.
• The part model answers were still present in qtype_formulas_answers.answer.
• The quiz review settings still allowed showing the right answer.

In the affected attempt, the step sequence looked like this:

• one complete step containing the actual response fields (0_0, 0_1, 1_0, etc.)
• one later gradedwrong step containing only -finish=1
• later mangrwrong / mangrpartial steps containing only manual grading fields such as -mark, -maxmark, -comment

This suggests the renderer is relying on the latest chronological step instead of the latest effective question response data.

Proposed fix

A possible fix would be in renderer.php, in response_is_same_as_submitted().

The method should use the latest effective question response data instead of relying on the latest chronological step, because manual regrading can add steps that contain grading metadata only and no actual response fields.

In practice, the renderer should use get_last_qt_data() when the latest steps do not contain question response data, so that feedback and correct answers are still shown consistently after manual regrading.

[PhilippImhof]

Hello @cmassoglia and thanks for the very detailed report.

I will look into this and prepare a fix. It will take me a few days to do it, though. The problem is most certainly linked to the recent bugfix, as you have also noticed.

[cmassoglia]

Hello @PhilippImhof, I am attaching a corrected version of renderer.php as an additional reference.

I validated this change locally, and in our environment it fixes the issue described above. I am sharing it only in case it is useful for your analysis and as a reference point for preparing an official fix in the plugin.

renderer.php

[PhilippImhof]

Thank you @cmassoglia

I have prepared a patch in PR #330, using a different approach. If you have time, you can already fetch the updated version from the linked branch and give it a try.

[cmassoglia]

@PhilippImhof

We tested the pull request in our environment and the issue now appears to be resolved.

After applying the patch, the feedback / correct answer is displayed correctly again after manual regrading, including in the scenario we originally reported for deferred feedback attempts.

From our side, the proposed fix looks good. Thank you for the correction.

[PhilippImhof]

Thanks for the perfect collaboration. The updated version will be available from the plugins directory in a moment.