I have a maven/tycho experiment with 2 orion server features at git://git.eclipse.org/gitroot/e4/org.eclipse.orion.server.git in the mavenExperiment branch.
If I check it out and cd to org.eclipse.orion.server/releng/org.eclipse.orion.server.aggregator I can run a mvn clean install and in ../org.eclipse.orion.server.repository (my eclipse-repository directory) it creates a valid p2 repo.
If I stay in the aggregator and run mvn clean install again it fails out with lots of compile errors. The bundles published to my local repository in $HOME/.m2/repository/org/eclipse/orion seem to be interfering with the second build. If I delete the $HOME/.m2/repository/org/eclipse/orion directory the build is once again successful.