1. `copy_cache` in `models.py` recursively copies the caches to environment, 
2. which in
```python
def _compute_related(self, records):
        """ Compute the related field ``self`` on ``records``. """
        others = records.sudo() if self.related_sudo else records
        if records.env != others.env:
            copy_cache(records - records.filtered('id'), others.env)
        values = list(others)
        for name in self.related[:-1]:
            values = [first(value[name]) for value in values]
        for record, value in zip(records, values):
            record[self.name] = value[self.related_field.name]
```
3. copies failing cache values that have been produce previously by this line:

`models.py : def _prefetch_field()`
```python

        try:
            # THIS ONE
            result = records.read([f.name for f in fs], load='_classic_write')
        except AccessError:
            # not all records may be accessible, try with only current record
            result = self.read([f.name for f in fs], load='_classic_write')
```
I checked it's exactly the same `FailedValue` object, which is later accessed without intent (not refreshed) by the fact that the buggy environment is copied to sudo (and not refreshed).


odoo/fields.py
value, or a function taking a recordset and returning a value; use
            ``default=None`` to discard default values for the field
        :param states: a dictionary mapping state values to lists of UI attribute-value
            pairs; possible attributes are: 'readonly', 'required', 'invisible'.
            Note: Any state-based condition requires the ``state`` field value to be
            available on the client-side UI. This is typically done by including it in
            the relevant views, possibly made invisible if not relevant for the
            end-user.
        :param groups: comma-separated list of group xml ids (string); this
            restricts the field access to the users of the given groups only
        :param bool copy: whether the field value should be copied when the record
            is duplicated (default: ``True`` for normal fields, ``False`` for
            ``one2many`` and computed fields, including property fields and
            related fields)
        :param string oldname: the previous name of this field, so that ORM can rename
            it automatically at migration
        .. _field-computed:
        .. rubric:: Computed fields
        One can define a field whose value is computed instead of simply being
        read from the database. The attributes that are specific to computed
        fields are given below. To define such a field, simply provide a value
        for the attribute ``compute``.
        :param compute: name of a method that computes the field
        :param inverse: name of a method that inverses the field (optional)
        :param search: name of a method that implement search on the field (optional)
        :param store: whether the field is stored in database (boolean, by
            default ``False`` on computed fields)
        :param compute_sudo: whether the field should be recomputed as superuser
            to bypass access rights (boolean, by default ``False``)
        The methods given for ``compute``, ``inverse`` and ``search`` are model