ProjectA triggers ProjectB
ProjectB has a RunParameter for ProjectA with a filter set for Successful Builds Only. The Run Parameter uses the PeepholePermalink to determine the LastSuccessful build.
When ProjectA completes successfully, it will trigger a build of ProjectB before the PeepholePermalink cache is updated. This causes the RunParameter to default to the previous successful build of ProjectA, not the one which has just completed.