Some Junit test results are randomly being dropped

### Jenkins and plugins versions report

Plugins

```text
JUnit Plugin - v1.29
```

### What Operating System are you using (both controller, and any agents involved in the problem)?

Controller - Linux (amd64)
Agent(s) - Windows 10 (amd64)

### Reproduction steps

1. Step 1: Run 14 tests in Jenkins in parallel shared across 9 Windows agents.
2. Step 2: All of the 14 tests generate an XML file which is successfully stashed.
3. Step 3: Post build, unstash the XML files,
4. Step 4: Execute the Junit test archive command with:
`junit allowEmptyResults: false, testResults: '**\\*.xml'`

### Expected Results

I expect to see 14 test results at all time.

### Actual Results

This is random, on some occasions I see all 14 test results output to Jenkins, and on other occasions I only see 13 or 12.

### Anything else?

We are currently running JUnit plugin v.129 on Jenkins, I am not certain if my issue is related to https://issues.jenkins.io/browse/JENKINS-48583, therefore I raised this issue.