When I go to "Manage Jenkins" and "Reload configuration from disk", the configuration for MsTestPublisher dissappears from the config.xml file for the job.

We have established that the following block exists in the config.xml before hitting "Reload configuration from disk" but after reloading it's gone.

<hudson.plugins.mstest.MSTestPublisher plugin="mstest@0.19">
  <testResultsFile>**/*.trx</testResultsFile>
  <buildTime>0</buildTime>
  <failOnError>true</failOnError>
  <keepLongStdio>true</keepLongStdio>
</hudson.plugins.mstest.MSTestPublisher>

We have other post-build steps defined in the configuration that remain in the file on configuration reloading, this particular one seems to be the only oddball.