Use the property originalValue instead of dictCfg in App.form.field.DictMultiDefault.

static/plugin_dbui/src/form/field/DictMultiDefault.js

@@ -86,7 +86,7 @@ Ext.define('App.form.field.DictMultiDefault', {
         "use strict";
         var me = this;
 
-        me.dictCfg = records.length ? records[0].get(me.dictField) : null;
+        me.originalValue = records.length ? records[0].get(me.dictField) : null;
 
         // load the current value if the key is back to the original one
         if (combo.getValue() === me.lastKey) {
@@ -94,7 +94,7 @@ Ext.define('App.form.field.DictMultiDefault', {
 
         // load default value
         } else {
-            me.grid.setSource(me.dictCfg);
+            me.grid.setSource(me.originalValue);
         }
     },