I have two Point of Sales. Both are occupied. When I try to access to Point of Sale dashboard, it is throwing following error:

Software Server Error

Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/Software/http.py", line 638, in _handle_exception return super(JsonRequest, self)._handle_exception(exception) File "/usr/lib/python2.7/dist-packages/Software/http.py", line 675, in dispatch result = self._call_function(**self.params) File "/usr/lib/python2.7/dist-packages/Software/http.py", line 331, in _call_function return checked_call(self.db, *args, **kwargs) File "/usr/lib/python2.7/dist-packages/Software/service/model.py", line 119, in wrapper return f(dbname, *args, **kwargs) File "/usr/lib/python2.7/dist-packages/Software/http.py", line 324, in checked_call result = self.endpoint(*a, **kw) File "/usr/lib/python2.7/dist-packages/Software/http.py", line 933, in __call__ return self.method(*args, **kw) File "/usr/lib/python2.7/dist-packages/Software/http.py", line 504, in response_wrap response = f(*args, **kw) File "/usr/lib/python2.7/dist-packages/Software/addons/web/controllers/main.py", line 820, in search_read return self.do_search_read(model, fields, offset, limit, domain, sort) File "/usr/lib/python2.7/dist-packages/Software/addons/web/controllers/main.py", line 842, in do_search_read offset=offset or 0, limit=limit or False, order=sort or False) File "/usr/lib/python2.7/dist-packages/Software/models.py", line 4671, in search_read result = records.read(fields) File "/usr/lib/python2.7/dist-packages/Software/models.py", line 3007, in read values[name] = field.convert_to_read(record[name], record, use_name_get) File "/usr/lib/python2.7/dist-packages/Software/models.py", line 5186, in __getitem__ return self._fields[key].__get__(self, type(self)) File "/usr/lib/python2.7/dist-packages/Software/fields.py", line 869, in __get__ self.determine_value(record) File "/usr/lib/python2.7/dist-packages/Software/fields.py", line 980, in determine_value self.compute_value(recs) File "/usr/lib/python2.7/dist-packages/Software/fields.py", line 935, in compute_value self._compute_value(records) File "/usr/lib/python2.7/dist-packages/Software/fields.py", line 926, in _compute_value getattr(records, self.compute)() File "/usr/lib/python2.7/dist-packages/Software/addons/point_of_sale/models/pos_config.py", line 162, in _compute_current_session_user pos_config.pos_session_username = pos_config.session_ids.filtered(lambda s: s.state == 'opened').user_id.name File "/usr/lib/python2.7/dist-packages/Software/fields.py", line 863, in __get__ record.ensure_one() File "/usr/lib/python2.7/dist-packages/Software/models.py", line 4798, in ensure_one raise ValueError("Expected singleton: %s" % self)ValueError: Expected singleton: pos.session(95, 94)

We have not customized anything.