Quiz and question banks

Hello, I am an Instructional Technologist/Moodle Administrator dealing with an issue following our system upgrade:

• Moodle Upgrade: 3.11 → 4.5.5

• CodeRunner Upgrade: 2021050800 → 2025052100

• Affected Course: One specific course whose content and question bank were imported from previous semesters (pre-upgrade). It is a "copy of a copy of a copy," with many CodeRunner questions created years ago (e.g., 2016).

• Scope: This is the only course at our institution that uses CodeRunner. We haven't received similar reports from any other courses.

• Functionality: CodeRunner itself runs normally for student quiz attempts.

The Problem Description

When the professor in this course attempts to use the "Duplicate" function on any existing or new quiz, it triggers an exponential duplication of only the CodeRunner question type within the Question Bank.

• The multiplication is geometric (2, 4, 8, 16...).

• The Question Bank has rapidly inflated from ∼300 questions to over 20,000.

• The duplication only affects CodeRunner questions. Other question types (Essay, Multiple Choice) are unaffected.

Test Results

I have conducted several tests to isolate the cause:

1. Test 1: In a brand-new, clean Moodle 4.5 course (no imported content), creating new quizzes and new CodeRunner questions works perfectly. Duplicating quizzes does not increase the question count.

2. Test 2: In a copy of the affected course, I deleted all old CodeRunner questions from the Question Bank. Duplicating a quiz no longer caused any extra questions to be created. Creating new quizzes and new CodeRunner questions subsequently works perfectly.

3. Test 3: In a copy of the affected course, I reduced the Question Bank to contain only other question types (Essay, MC) and one single old CodeRunner question. Duplicating any quiz (regardless of whether it contains the old CodeRunner question or not) still triggered the geometric duplication of that single CodeRunner question.

Other Details

• The duplicated questions are visually identical to the originals (same name, creator, timestamp).
• Not all CodeRunner questions in the bank were affected by the duplication, but a substantial number were. 
• This duplication pedagogy was used by the professor in the same course before the upgrade without any issue.
• An "undefined" message always pops up after the duplication finishes.
• Our system administrator did not notice error messages in the server logs during the duplication attempts, although the Moodle process hangs.
• The filtering options for the Question Bank are currently grayed out across our Moodle site (although enabled in the backend). (Any advice on this separate issue is appreciated as well).

Questions for the Community

I've looked at other threads regarding similar duplication bugs, such as https://moodle.org/mod/forum/discuss.php?d=469704, https://moodle.org/mod/forum/discuss.php?d=469874, and https://moodle.org/mod/forum/discuss.php?d=468327. While previous reports involved broader question types, our issue seems to be confined to CodeRunner questions.

1. Any insights on this CodeRunner-specific behavior? 

2. Upgrading to Moodle 4.5.6 has been suggested in the forum as a general solution for this bug, but we will need time for change management. While we are in that process, are there any other recommendations or insights?

Thank you for any insight you can provide!