Custom assignment block not editable in Change Document (SM_CRM)

Hello Experts!

I created a custom assignment block in the ChaRM change request (ZMCR) and another one in the change document (ZMMJ).  The one I created in ZMCR works fine. The fields are editable and save/auto-fill as expected.   However, the field in the change document's assignment block does not.  When the charm document is edit mode, the field stays in display mode.   I created the field the same as I did in the Change Request.

Here are the field properties...

Any thoughts on why the field isn't editable in the change document?

Thanks! Hoping to award points!!!