How to release Xtext 2.13 project to Maven Central - maven

Question

I have created an Xtext Language and I want to release it to Maven central. I have already prepared the release with:
mvn release:prepare
My first try to release with
mvn release:perform
failed due to the strict Javadoc checking (Xtext generates some tags that are not understood by the javadoc plugin). So I added this to my pluginManagement section, to silence the errors and convert them into warnings:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
<version>2.9</version>
<configuration>
<additionalparam>-Xdoclint:none</additionalparam>
</configuration>
<executions>
<execution>
<id>attach-javadocs</id>
<goals>
<goal>jar</goal>
</goals>
</execution>
</executions>
</plugin>
However, this fails with
[ERROR] Failed to execute goal org.eclipse.tycho:tycho-p2-plugin:1.0.0:p2-metadata (attach-p2-metadata) on project com.hribol.bromium.dsl: Execution attach-p2-metadata of goal org.eclipse.tycho:tycho-p2-plugin:1.0.0:p2-metadata failed.
What could be the reason for this error? It happens immediately after the warnings for the Javadoc, if that matters.
EDIT: After I manually executed the steps from the Maven log, I got the full stack trace:
[INFO] [ERROR] Failed to execute goal org.eclipse.tycho:tycho-p2-
plugin:1.1.0-SNAPSHOT:p2-metadata (attach-p2-metadata) on project com.hribol.bromium.dsl: Execution attach-p2-metadata of goal org.eclipse.tycho:tycho-p2-plugin:1.1.0-SNAPSHOT:p2-metadata failed.: IllegalArgumentException -> [Help 1]
[INFO] org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.eclipse.tycho:tycho-p2-plugin:1.1.0-SNAPSHOT:p2-metadata (attach-p2-metadata) on project com.hribol.bromium.dsl: Execution attach-p2-metadata of goal org.eclipse.tycho:tycho-p2-plugin:1.1.0-SNAPSHOT:p2-metadata failed.
[INFO] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:213)
[INFO] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:154)
[INFO] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:146)
[INFO] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:117)
[INFO] at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:81)
[INFO] at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
[INFO] at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
[INFO] at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:309)
[INFO] at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:194)
[INFO] at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:107)
[INFO] at org.apache.maven.cli.MavenCli.execute(MavenCli.java:993)
[INFO] at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:345)
[INFO] at org.apache.maven.cli.MavenCli.main(MavenCli.java:191)
[INFO] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[INFO] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[INFO] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[INFO] at java.lang.reflect.Method.invoke(Method.java:498)
[INFO] at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
[INFO] at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
[INFO] at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
[INFO] at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
[INFO] Caused by: org.apache.maven.plugin.PluginExecutionException: Execution attach-p2-metadata of goal org.eclipse.tycho:tycho-p2-plugin:1.1.0-SNAPSHOT:p2-metadata failed.
[INFO] at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
[INFO] at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
[INFO] ... 20 more
[INFO] Caused by: java.lang.IllegalArgumentException
[INFO] at org.eclipse.tycho.p2.impl.publisher.P2GeneratorImpl.getCanonicalArtifact(P2GeneratorImpl.java:193)
[INFO] at org.eclipse.tycho.p2.impl.publisher.P2GeneratorImpl.generateMetadata(P2GeneratorImpl.java:146)
[INFO] at org.eclipse.tycho.plugins.p2.P2MetadataMojo.attachP2Metadata(P2MetadataMojo.java:149)
[INFO] at org.eclipse.tycho.plugins.p2.P2MetadataMojo.execute(P2MetadataMojo.java:108)
[INFO] at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
[INFO] ... 21 more
EDIT 2: After following the workaround from here - moving the tycho p2 plugin only to the projects that need it - feature, repository and target, the build no longer breaks with IllegalArgumentException. This time it fails in the signing phase, because a file named p2content.xml is missing. Does anyone know what could be the reason? If I just build the project with mvn clean install the p2content.xml is indeed created, so I think that is probably due to some wrong execution order.