Jenkins "POM_VERSION" variable does not reset from build to build - maven

Question

Following Jenkins documentation jenkins docs
I can use the POM_VERSION environment variable to take the current version from the pom file.
But for some reason the POM_VERSION environment variable is not being refreshed from build to build. for example:
I changed the version number manually but the build number that exported was the last from the previous build.
From my python script:
print 'Current version is ' + os.environ['POM_VERSION']
which gives the following log Current version is 0.1.5 which is clearly wrong because i changed it. you can further see it in my maven versions goal output:
[INFO]
[INFO] --- versions-maven-plugin:2.1:set (default-cli) # ep-reporter ---
[INFO] Searching for local aggregator root...
[INFO] Local aggregation root: /var/lib/jenkins/jobs/exchange-planner- reporter/workspace
[INFO] Processing com.exelate:ep-reporter
[INFO] Updating project com.company:ep-reporter
[INFO] from version 0.1.8 to 0.1.6
Props: {project.version=0.1.6, project.artifactId=ep-reporter, project.groupId=com.company}
note that it went from 0.1.5 because i have a script that advances it. but maven clearly states that its changing it from 0.1.8 to 0.1.6 which is not what POM_VERSION says
Thanks.

Answer 1

That environment variable is set at the time Jenkins first reads your POM file. You are clearly changing it during the build.
If you are changing it during the build, you know what you are changing to, and you should use the same mechanism to display it later.

Answer 2

I had the same problem and I resolved it by setting "Check-out Strategy" option to "Always checkout a fresh copy" in Source Code Management section.