I have repacked xpp.jar to see of this resolved the problem. It was repacked from a signed jar to an unsigned jar. Basically I unpacked the jar and repacked it. This lead to a significant smaller jar. However, this did not resolve the problem BUT I did not revert that change. After that I committed the real solution which was adding some line in the build.properties file.
I wonder if we should revert the repackaged xpp.jar to the original version to avoid any regression? How likely is it that the tests take care of this case?