lightning:recordForm does not display correctly on Home Page

Hi,
I am trying to implement the new lightning:recordForm for a component that need to diplay on Home page. The result does not look right (fields are packed on the left of the screen as below) on Home page but diplay correctly on another custom lightning tab.
Do I missed something or is it a bug?

User-added image

My code:

<aura:component implements="force:appHostable,flexipage:availableForAllPageTypes,flexipage:availableForRecordHome,force:hasRecordId,force:lightningQuickAction" access="global" >
    
    <aura:attribute name="fields" type="List" default="Name,OwnerId,CSB_Name__c,Date__c,Overdue_Tasks__c,Unactioned_Emails__c,Comment__c"/>
    
    <lightning:card iconName="custom:custom19" title="Create New Workload" >
        <div class="slds-p-left_large slds-p-right_medium">	
            <lightning:recordForm aura:id="form"
                                  objectApiName="Workload_Register__c" 
                                  fields = "{!v.fields}"
                                  columns = "1"
                                  mode = "Edit"
                                  onsubmit = "{!c.handleSubmit}"
                                  onsuccess="{!c.handleSuccess}"                          
                                  onerror="{!c.onError}"
                                  />
        </div>
    </lightning:card>  
    
</aura:component>

Thank you in advance for your help.
Sylvie