Update Method in BADI Implementation Triggering twice

Hello Friends,

I implemented BADI BADI_LE_SHIPMENT and  using IN_UPDATE method. I put my code in IN_UPDATE method.

My requirement is to create a new task in separate session after shipment is saved. In new session(FM new task) we are updating billing docs and sending outputs and DRP. It works fine but not all the times .

When an Sales Order is locked , and shipment is saved, implementation is called twice. Triggering two new sessions and executes the FM in each session.

I tried  setting flag with Class variable ,  export/import to memory options. It did not work .

Could you please help me how to restrict implementation execution for the second time which stops triggering the FM in new task for the second time.

Thanks.

Krishna