On several test instances I noticed that when trying to delete a run from a Matrix project that the confirmDelete form shown is that of Jenkins core and not the one from the mAtrix Project.

The root cause might be that Matric project defines its own confirmDelete.jelly and puts it in .../resources/hudson/model/Run.

My guess it that when the resource is looked up it can happen that the one from core is found first in the classpath.

When running jenkins via hpi:run from the matrix project sources everything works as expected.