The following change seems to be the fix:
form.py line 298: (Checkbox.render)
substitute: attrs['value'] = self.value
by: attrs['value'] = self.value or self.name
The following change seems to be the fix:
form.py line 298: (Checkbox.render)
substitute:
attrs['value'] = self.value
by:
attrs['value'] = self.value or self.name