Ok,

Je pensais que vous parliez du model website.page et pas website.controller.page.

Cette feature de website.controller.page est assez technique, et pas prévu d'etre utilisé sans Studio, l'UI n'est pas prévu pour et l'uX donc tres difficile. Il est en standard dans website pour être utilisable par les module data / industries (et donc configurer en xml directement)

Ce menu n'est plus affiché par défaut, pour éviter la confusion. 

https://github.com/odoo/odoo/commit/d08c9aab4249511151e9d4db78cdc1bf1e792016

Bien à vous

Hello Jeremy,

L'erreur complète est la suivante : 
Rencontrée sur saas odoo.com et sur SH aussi.

Merci

RPC_ERROR
Odoo Server Error
Traceback (most recent call last):
  File "/home/odoo/src/odoo/17.0/odoo/models.py", line 5841, in ensure_one
    _id, = self._ids
ValueError: not enough values to unpack (expected 1, got 0)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/odoo/src/odoo/17.0/odoo/http.py", line 1722, in _serve_db
    return service_model.retrying(self._serve_ir_http, self.env)
  File "/home/odoo/src/odoo/17.0/odoo/service/model.py", line 133, in retrying
    result = func()
  File "/home/odoo/src/odoo/17.0/odoo/http.py", line 1749, in _serve_ir_http
    response = self.dispatcher.dispatch(rule.endpoint, args)
  File "/home/odoo/src/odoo/17.0/odoo/http.py", line 1953, in dispatch
    result = self.request.registry['ir.http']._dispatch(endpoint)
  File "/home/odoo/src/odoo/17.0/addons/website/models/ir_http.py", line 235, in _dispatch
    response = super()._dispatch(endpoint)
  File "/home/odoo/src/odoo/17.0/odoo/addons/base/models/ir_http.py", line 222, in _dispatch
    result = endpoint(**request.params)
  File "/home/odoo/src/odoo/17.0/odoo/http.py", line 722, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo/src/odoo/17.0/addons/web/controllers/dataset.py", line 24, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/odoo/src/odoo/17.0/addons/web/controllers/dataset.py", line 20, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/home/odoo/src/odoo/17.0/odoo/api.py", line 468, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/home/odoo/src/odoo/17.0/odoo/api.py", line 453, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/home/odoo/src/odoo/17.0/addons/web/models/models.py", line 1021, in onchange
    record[parent_name]._update_cache({field_name: record[field_name]})
  File "/home/odoo/src/odoo/17.0/odoo/models.py", line 5985, in _update_cache
    self.ensure_one()
  File "/home/odoo/src/odoo/17.0/odoo/models.py", line 5844, in ensure_one
    raise ValueError("Expected singleton: %s" % self)
ValueError: Expected singleton: ir.ui.view()

The above server error caused the following client error:
RPC_ERROR: Odoo Server Error
    at makeErrorFromResponse (https://ekwela.odoo.com/web/assets/1/4021c55/web.assets_web_dark.min.js:2872:163)
    at XMLHttpRequest. (https://ekwela.odoo.com/web/assets/1/4021c55/web.assets_web_dark.min.js:2876:13)