Problem with entity browser inside IEF when replacing, or remove / add

I have an ECK entity nested in another ECK entity with IEF. In my nested entity, I have an entity reference field that uses Entity Browser for selecting entities to reference.

Parent
- Child
- - ER field ( entity browser )

When adding a new reference to the Child entity, I can open the entity browser, make select, save.

However, if I edit an existing child entity, removing the ER, entity browser does not open, I seem to get a partial page refresh.

NOTE: when I create a new Child, I am able to add / remove / replace ERs just fine. It's only when I save, then edit the Parent that the problem appears.

I do not get any PHP or JS errors. The only difference I have noticed is the response from the ajax request.

Response with a new Child ER: ( working )

[  
   {  
      "command":"update_build_id",
      "old":"form-MR1z7sxf7o_x2p504Ee0UcfUCP-wAPLyA6Qa2ulgRkQ",
      "new":"form-0JNBPqvopjUIxBM5vGiY6GfkAvKhhy1ycZf180Iwi8k"
   },
   {  
      "command":"openDialog",
      "selector":"#field-bookings-bookings-accommodation-security-dialog--fYGn7doAT-I",
      "settings":null,
      "data":"\u003Cdiv class=\u0022ajax-progress-throbber\u0022\u003E\u003C\/div\u003E\u003Ciframe src=\u0022\/entity-browser\/modal\/bookings_accommodation_security?uuid=7d84f0247035a4f0839cd448140397bf625ccd3b\u0026amp;original_path=\/booking\/66\/edit\u0022 class=\u0022entity-browser-modal-iframe\u0022 width=\u0022100%\u0022 frameborder=\u00220\u0022 style=\u0022padding:0; position:relative; z-index:10002;\u0022 name=\u0022entity_browser_iframe_bookings_accommodation_security\u0022 id=\u0022entity_browser_iframe_bookings_accommodation_security\u0022\u003E\u003C\/iframe\u003E\n",
      "dialogOptions":{  
         "width":"auto",
         "height":"auto",
         "modal":true,
         "maxWidth":"",
         "maxHeight":"",
         "fluid":1,
         "autoResize":0,
         "resizable":0,
         "classes":{  
            "ui-dialog":"entity-browser-modal"
         },
         "title":"Select Accommodation Booking"
      }
   }
]

Response when replacing ( or Remove / Add ) an existing Child ER and Entity Browser does not open:

[  
   {  
      "command":"update_build_id",
      "old":"form-5-dCuJ01a-L-jAoPhbTp2QEEbTILD9wXEj4X9V1p3CU",
      "new":"form-BvDTGfxgkAyEdO3jB7fKp-fN0WU7eG6M6FdZFc0WeTo"
   },
   {  
      "command":"insert",
      "method":"replaceWith",
      "selector":null,
      "data":"\u003Cspan class=\u0022ajax-new-content\u0022\u003E\u003C\/span\u003E",
      "settings":null
   }
]

I only notice this problem on nested ECK entities. When I edit the ECK entities directly, entity browser works as expected. On nested Paragraphs, it seems to work fine in my basic tests.

I am not sure what additional information would be useful.