Odoo 16 one2many treeview not full size of <group>

I want to show multiple one2may treeviews in a form view.  The problem is that the treeviews will not show the full size of the group, but the header of the group is shown correctly. 

Here is the code:

<notebook>
                    <page string="Planing">
                      
                      <group col="2">
                        
                        <group string="Timesheet">
                                
                              
                               
                                
                                    <field name="timesheet_ids" widget="one2many" nolabel="1">;
                                        <tree editable="bottom">
                                            <field name="time_event_type"/>
                                            <field name="date"/>
                                            <field name="begin_time" widget="float_time"/>
                                            <field name="end_time" widget="float_time"/>
                                            <field name="total_hours" widget="float_time" readonly="true"/>
                                        </tree>
                                    </field>
                                </group>
                        
                          
                          
                            <group string="Daily Allowance">

                                  
                                    <field name="planned_daily_allowance_ids" nolabel="1">
                                        <tree editable="bottom">
                                            <field name="daily_allowance"/>
                                            <field name="da_description"/>
                                            <field name="daily_allowance_amount"/>
                                            <field name="number_of_days"/>
                                            <field name="number_of_employee"/>
                                            <field name="correct_number_of_employee"/>
                                            <field name="line_total"/>
                                            <field name="event_master_id"/>

                                        </tree>
                                    </field>
                            </group>


                     </group>

                      
                     </page>

#More Pages
</notebook>

Here you can see the view in the browser: enter image description here

I have tried all kinds of col values and testets with colspan. But no change fixed it.  Does someone have an idea for a solution?  Thanks

Try to set colspan="2" on the field tag

Groups define 2 columns and most direct children of groups take a single column.

The number of columns in a group can be customized using the col attribute, the number of columns taken by an element can be customized using colspan.

You can find more details in the Structural components documentation section