The problem cause of the problem is in the debug output you have linked. Compare the output before the failure ...
[DEBUG] Extension realms for project mybundle:mybundle.myproject.target:eclipse-target-definition:0.0.1-SNAPSHOT: (none)
[DEBUG] Looking up lifecyle mappings for packaging eclipse-target-definition from ClassRealm[plexus.core, parent: null]
... with the output of a previous, successful lookup of one of Tycho's packaging types:
[DEBUG] Extension realms for project mybundle:mybundle.myproject.repository:eclipse-repository:0.0.1-SNAPSHOT: [ClassRealm[extension>org.eclipse.tycho:tycho-maven-plugin:0.18.1, parent: sun.misc.Launcher$AppClassLoader@affc70]]
[DEBUG] Looking up lifecyle mappings for packaging eclipse-repository from ClassRealm[project>mybundle:mybundle.myproject.parent:0.0.1-SNAPSHOT, parent: ClassRealm[maven.api, parent: null]]
Here is what you can read from the output: The project mybundle.myproject.target
doesn't have any build extensions (i.e. in particular not the Tycho build extension) configured. From the second line of debug output, this seems to be because the project doesn't have the parent mybundle.myproject.parent
configured like the other modules.