User login "Exception: Data Binding update failed with 1 error"

It is at the user login.

the logs are this

New browser session from Slough, United Kingdom.
Exception: Data Binding update failed with 1 error. Did you initialise all data binding sources before initialising this component? at Form1.RowTemplate1, line 15
Exception: Data Binding update failed with 1 error. Did you initialise all data binding sources before initialising this component? at Form1.RowTemplate1, line 15called from Form1, line 28called from Form1, line 23
Exception: Data Binding update failed with 1 error. Did you initialise all data binding sources before initialising this component? at Form1.RowTemplate1, line 15
Exception: Data Binding update failed with 1 error. Did you initialise all data binding sources before initialising this component? at Form1.RowTemplate1, line 15called from Form1, line 28called from Form1, line 23

This is the code in the Form1;

class RowTemplate1(RowTemplate1Template):
  def __init__(self, **properties):
    # Set Form properties and Data Bindings.
    self.init_components(**properties)

    # Any code you write here will run when the form opens.
    
  def delete_btn_click(self, **event_args):
    """This method is called when the button is clicked"""
    if confirm(f"Delete file {self.item['file'].name}?"):
      anvil.server.call('delete_file', self.item)
      self.parent.raise_event('x-refresh')

#   def chart_btn_click(self, **event_args):
#     """This method is called when the button is clicked"""
#     open_form('Dashboard01', item={'file':self.item['file'], 'computed_file':self.item['computed_file'], 'analysis_time':self.item['analysis_time']})

  def link_1_click(self, **event_args):
    """This method is called when the link is clicked"""
    pass

I had thought the def chart_btn_click() might have been causing a problem. I commented that out last night with no apparent effect on the error

The user tried again this morning and got this;

For the avoidance of doubt the user did not have Arabic as a setting in the browser.

I am not sure where to go after that.