button "attach" does not work when added to Z bsp component

Hello Experts,

I add the attachment assignment block to my Z bsp component but when I try to attach document, it's not added to the attachment table.

I made a breakpoint in the GS_CM/AddDoc view, on the outbound plugs "OP_ADDDOC2DOCLIST" as shown below

and after execution, the gr_added_documents is always INITIAL

But when I try to attach document in standard component, this field is not initial.

Could you please help.

Thank you in advance.