Celery chord of chords of chords - top callback not called

I'm having a complicated workflow which is chord of chords that spawn chords. the top chord callback is not called. all inner tasks have completed.

This is the workflow:

work = chain(taskA, taskB)
return work()
taskB: creates the following workflow:
work = group(**group(taskC, taskD)** | taskE), **group(taskC, taskD**) | taskE)) | taskF
return work()

and each inner group(marked with **) creates another chord = group(taskG, taskH, ..) | taskV

Does anyone know how to solve this challege? maybe I should change my workflow.

thanks