Test failure: System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1584491
Build error leg or test failing: System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync

## Error Message

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync [FAIL]",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1584491
**Error message validated:** `[System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync [FAIL]`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 9/7/2026 1:59:56 AM UTC

### Report

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1584491](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1584491)|dotnet/runtime|[System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1584491&view=ms.vss-test-web.build-test-results-tab&runId=43717784&resultId=103052)||
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|0|1|

Start with the linked Azure DevOps build and the failing System.ComponentModel.EventBasedAsync.Tests.BackgroundWorkerTests.TestCancelAsync test. Review its test output and surrounding test context to identify the failure cause; done means the test passes reliably and the known-issue report no longer matches unexplained failures.

Written by the indexing model from the issue text.