PE results are not uploaded due to a bug of Celery.

PE results are not uploaded due to the following bug of Celery.

With the following script,

(
    group(
        A.si(),
        B.si()
    )
    |
    C.si()
    |
    D.si()
    |
    chain(E.si(), F.si(), G.si())
).delay()

only A, B, C and D are executed. This is the case even when another task sits before group. E, F and G will be executed when C or D is removed, or with the following script.

(
    group(
        A.si(),
        B.si()
    )
    |
    C.si()
    |
    D.si()
    |
    E.si()
    |
    F.si()
    |
    G.si())
).delay()