[SalesForce] Dependent picklist does not get enabled when the parent picklist’s value is set through controller

I am using lightning:recordEditForm and listing the various field I need to create in lightning:inputField. Two of these are dependent picklists, meaning only if the parent picklist has been selected the child will get enabled with associated values. Here is the code;

<lightning:recordEditForm aura:id="contactCreateForm" objectApiName="Contact" recordTypeId="{!v.individualRecordTypeId}"
                        onsubmit="{!c.onSubmit}"
                        onload="{!c.onLoad}"
                        onsuccess="{!c.onSuccess}"
                        onerror="{!c.onError}"
                        >
                            <lightning:messages />
                            <lightning:inputField aura:id="ccf_FirstName" fieldName="FirstName" />
                            <lightning:inputField aura:id="ccf_LastName" fieldName="LastName" />

                            <lightning:inputField aura:id="ccf_nickname" fieldName="Nickname__c" />
                            <lightning:inputField aura:id="ccf_email" fieldName="Email" />

                            <lightning:inputField aura:id="ccf_ReportsToId" fieldName="ReportsToId" />
                            <lightning:inputField aura:id="ccf_Firm_Description__c" fieldName="Firm_Description__c" />
                            <lightning:inputField aura:id="ccf_Userclass__c" fieldName="Userclass__c" />
                            <div align="center">
                                <lightning:button class="slds-m-top_small" variant="brand" type="submit" label="Save" />
                                <lightning:button class="slds-m-top_small" variant="neutral" label="Cancel" onclick="{!c.handleCancel}" />
                            </div>
                        </lightning:recordEditForm

I am setting the value of the parent picklist in the onLoad() event of the lightning:recordEditForm. This gets populated in the UI as expected, however, on the population of parent picklist, I expect the child picklist to get enabled which does not happen.

 onLoad: function(component, event, helper){
   component.find("ccf_Firm_Description__c").set("v.value", component.get("v.accountObj.Location_Firm_Description__c"));
   component.find("ccf_Userclass__c").set("v.disabled",false);
 }

I want to make the child picklist enabled. I tried to set the v.disabled property of the lightning:inputField to false. This throws an internal error.

Error:

Uncaught render threw an error in 'lightning:inputField' [Cannot read property 'config' of undefined] 
throws at https://factset--devpro.lightning.force.com/auraFW/javascript/fm7mXFzeJAXPkqJAjx6Qpw/aura_proddebug.js:24283

I tried doing a $A.get('e.force:refreshView').fire(); on afterRender in the renderer. Doesn't work either. Using jQuery to enable it won't work either because of the locker service and disabling it for my org is not an option. I wanted to know if I'm missing something before raising a case with Salesforce.

Any help on how to enable the dependant picklist is much appreciated.