We create a matrix project which gets its dynamic axes from build parameter. The job is doeing nothing instead printing some messages and wait an amount of time. Now we create an upstream project. This project calls the matrix project with different axis as a build parameter. This means we call the project and this starts parallel the matrix project with diferent axis.
The projects are run with the correct matrix, but sometimes the job configuration contains the matrix values from another parallel build. This is visible if you compare the console output with the generated links in the build status UI.
We attached the job configurations and one build.xml where you can see that the builded matrix differs from the given build parameter.