Error:
Odoo Server Error

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 654, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 312, in _handle_exception
    raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
  File "/usr/lib/python3/dist-packages/odoo/tools/pycompat.py", line 87, in reraise
    raise value
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 696, in dispatch
    result = self._call_function(**self.params)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 344, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/service/model.py", line 97, in wrapper
    return f(dbname, *args, **kwargs)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 337, in checked_call
    result = self.endpoint(*a, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 939, in __call__
    return self.method(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/http.py", line 517, in response_wrap
    response = f(*args, **kw)
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 966, in call_button
    action = self._call_kw(model, method, args, {})
  File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/main.py", line 954, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 749, in call_kw
    return _call_kw_multi(method, model, args, kwargs)
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 736, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/var/lib/odoo/addons/12.0/METQUAY_API_V3/models/sale_order.py", line 112, in create_customer_instrument_from_orderline
    api_url_data = "/FlexicalERP/rest/customerInstrument/createCustomerInstrument" if not self.exported_using_api else "/FlexicalERP/rest/customerInstrument/updateCustomerInstrument"
AttributeError: 'sale.order' object has no attribute 'exported_using_api'