In writing my own ComputedFolder any attempts to create a Folder as a child during computeChildren results in the folder being physically written to disk but maxing multiple CPU cores and hanging Jenkins. This issue persists through Jenkins restarts and any Job created with this structure causes the same issue. It does not hang Jenkins until the Job is navigated to on reboot.
A simple test case of this can be done by extending ComputedFolder, creating a Folder (with the computed as it parent) and using the observer methods to register it. Manually using itemsPut also causes the same issue - Jenkins will hang if you try to navigate to view that folder.