Error #725. RBE2 has rotational rigid body modes in all three directions.

Hello all,

I am working on a model and while running it on optistruct the following error occurs:

*** ERROR # 725 ***
An invalid rigid element.
This RBE2 has rotational rigid body modes in all three directions.
RBE2 element id = 436463
independent grid id = 83349
Note: If this rigid element is also connected with other rigid elements,
then this error means that there is rigid body mode or mechanism
in this rigid element chain due to the lack of connected structural elements.

Can anyone tell me why is this error occurring and what can I do to correct it?

I have also attached the HM file of my model for refrence.

Thanks