When building with Jenkins the PostBuildStep fails with an Exception

17:01:07 ERROR: Step ‘Post build task’ aborted due to exception:
17:01:07 java.nio.charset.UnmappableCharacterException: Input length = 1
17:01:07     at java.nio.charset.CoderResult.throwException(CoderResult.java:282)
17:01:07     at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:339)
17:01:07     at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
17:01:07     at java.io.InputStreamReader.read(InputStreamReader.java:184)
17:01:07     at java.io.BufferedReader.fill(BufferedReader.java:161)
17:01:07     at java.io.BufferedReader.read1(BufferedReader.java:212)
17:01:07     at java.io.BufferedReader.read(BufferedReader.java:286)
17:01:07     at hudson.Util.loadFile(Util.java:199)
17:01:07     at hudson.model.Run.getLog(Run.java:1953)
17:01:07     at hudson.plugins.postbuildtask.PostbuildTask.perform(PostbuildTask.java:99)
17:01:07     at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
17:01:07     at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:744)
17:01:07     at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:690)
17:01:07     at hudson.model.Build$BuildExecution.post2(Build.java:186)
17:01:07     at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:635)
17:01:07     at hudson.model.Run.execute(Run.java:1752)
17:01:07     at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
17:01:07     at hudson.model.ResourceController.execute(ResourceController.java:97)
17:01:07     at hudson.model.Executor.run(Executor.java:429)

How do I find more information on this and the cause of this error?
The build failed without any configuration changes or updates on jenkins.