HI, for long time nobody was doing any kind of changes in modules/code, etc. and out of sudden I get a ODOO SERVER error, In PROJECTs APP (v16, CE, tried to restart and in Inkognito window, under mulptiple users, same result : ANYBODY can  HELP? }it happens only in KANBAN view, list view is OK) 
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RPC_ERROR
Odoo Server Error
Traceback (most recent call last):
File "/opt/odoo/odoo_prod/odoo/odoo/http.py", line 1579, in _serve_db
return service_model.retrying(self._serve_ir_http, self.env)
File "/opt/odoo/odoo_prod/odoo/odoo/service/model.py", line 134, in retrying
result = func()
File "/opt/odoo/odoo_prod/odoo/odoo/http.py", line 1608, in _serve_ir_http
response = self.dispatcher.dispatch(rule.endpoint, args)
File "/opt/odoo/odoo_prod/odoo/odoo/http.py", line 1805, in dispatch
result = self.request.registry['ir.http']._dispatch(endpoint)
File "/opt/odoo/odoo_prod/odoo/addons/website/models/ir_http.py", line 235, in _dispatch
response = super()._dispatch(endpoint)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_http.py", line 144, in _dispatch
result = endpoint(**request.params)
File "/opt/odoo/odoo_prod/odoo/odoo/http.py", line 698, in route_wrapper
result = endpoint(self, *args, **params_ok)
File "/opt/odoo/odoo_prod/odoo/addons/web/controllers/dataset.py", line 46, in call_button
action = self._call_kw(model, method, args, kwargs)
File "/opt/odoo/odoo_prod/odoo/addons/web/controllers/dataset.py", line 33, in _call_kw
return call_kw(request.env[model], method, args, kwargs)
File "/opt/odoo/odoo_prod/odoo/odoo/api.py", line 461, in call_kw
result = _call_kw_multi(method, model, args, kwargs)
File "/opt/odoo/odoo_prod/odoo/odoo/api.py", line 448, in _call_kw_multi
result = method(recs, *args, **kwargs)
File "/opt/odoo/odoo_prod/odoo/addons/project/models/project.py", line 769, in action_view_tasks
action = self.env['ir.actions.act_window'].with_context({'active_id': self.id})._for_xml_id('project.act_project_project_2_project_task_all')
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_actions.py", line 164, in _for_xml_id
return record._get_action_dict()
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_actions.py", line 173, in _get_action_dict
for field, value in self.sudo().read()[0].items()
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_actions.py", line 272, in read
result = super(IrActionsActWindow, self).read(fields, load=load)
File "/opt/odoo/odoo_prod/odoo/odoo/models.py", line 2994, in read
return self._read_format(fnames=fields, load=load)
File "/opt/odoo/odoo_prod/odoo/odoo/models.py", line 3132, in _read_format
vals[name] = convert(record[name], record, use_name_get)
File "/opt/odoo/odoo_prod/odoo/odoo/models.py", line 5851, in __getitem__
return self._fields[key].__get__(self, type(self))
File "/opt/odoo/odoo_prod/odoo/odoo/fields.py", line 1188, in __get__
self.compute_value(recs)
File "/opt/odoo/odoo_prod/odoo/odoo/fields.py", line 1347, in compute_value
records._compute_field_value(self)
File "/opt/odoo/odoo_prod/odoo/odoo/models.py", line 4196, in _compute_field_value
getattr(self, field.compute)()
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_actions.py", line 240, in _compute_search_view
fvg = self.env[act.res_model].get_view(act.search_view_id.id, 'search')
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 2665, in get_view
result = dict(self._get_view_cache(view_id, view_type, **options))
File "", line 2, in _get_view_cache
File "/opt/odoo/odoo_prod/odoo/odoo/tools/cache.py", line 90, in lookup
value = d[key] = self.method(*args, **kwargs)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 2625, in _get_view_cache
arch, view = self._get_view(view_id, view_type, **options)
File "/opt/odoo/odoo_prod/odoo/addons/hr_timesheet/models/project.py", line 393, in _get_view
arch, view = super()._get_view(view_id, view_type, **options)
File "/opt/odoo/odoo_prod/odoo/addons/project/models/project.py", line 1366, in _get_view
arch, view = super()._get_view(view_id, view_type, **options)
File "/opt/odoo/odoo_prod/odoo/addons/web/models/models.py", line 241, in _get_view
arch, view = super()._get_view(view_id, view_type, **options)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 2572, in _get_view
arch = view._get_combined_arch()
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 991, in _get_combined_arch
arch = root.with_prefetch(tree_views._prefetch_ids)._combine(hierarchy)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 932, in _combine
combined_arch = view.apply_inheritance_specs(combined_arch, arch)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 869, in apply_inheritance_specs
self._raise_view_error(str(e), specs_tree)
File "/opt/odoo/odoo_prod/odoo/odoo/addons/base/models/ir_ui_view.py", line 746, in _raise_view_error
raise err from from_exception
ValueError: Element '' cannot be located in parent view

The above server error caused the following client error:
RPC_ERROR: Odoo Server Error
at makeErrorFromResponse (https://odoo.ledeco.sk/web/assets/9216-61cffd3/web.assets_backend.min.js:968:163)
at XMLHttpRequest. (https://odoo.ledeco.sk/web/assets/9216-61cffd3/web.assets_backend.min.js:975:13)