Reproduce and fix a bug properly

Forces a failing test before any fix, so you find out whether the bug was real and whether it stayed fixed.

Fix this bug using a reproduce-first workflow.

BUG REPORT
- What I did: [STEPS]
- What I expected: [EXPECTED]
- What happened: [ACTUAL]
- Environment: [BROWSER / VERSION / ROUTE]

PROCESS
1. Locate the code paths involved and quote the relevant lines with file paths.
2. State your hypothesis for the root cause in one sentence.
3. Write a failing test that reproduces the bug. Run it and paste the failure.
4. Fix the smallest amount of code that makes the test pass.
5. Run the whole test suite plus typecheck and paste the output.
6. Tell me whether the root cause exists anywhere else in the codebase.

RULES
- No fix before a failing test exists.
- Do not change unrelated files, formatting or dependencies.
- If the hypothesis is wrong after the test, say so and start again at step 2.