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
super(Selection, self).__init__(selection=selection, string=string, **kwargs)
    @property
    def column_type(self):
        if (self.selection and
                isinstance(self.selection, list) and
                isinstance(self.selection[0][0], int)):
            return ('int4', 'integer')
        else:
            return ('varchar', pg_varchar())
    def _setup_regular_base(self, model):
        super(Selection, self)._setup_regular_base(model)
        assert self.selection is not None, "Field %s without selection" % self
    def _setup_related_full(self, model):
        super(Selection, self)._setup_related_full(model)
        
        field = self.related_field
        self.selection = lambda model: field._description_selection(model.env)
    def _setup_attrs(self, model, name):
        super(Selection, self)._setup_attrs(model, name)
        
        for field in reversed(resolve_mro(model, name, self._can_setup_from)):
            
            
            if 'selection' in field.args:
                self.selection = field.args['selection']
            if 'selection_add' in field.args:
                
                selection_add = field.args['selection_add']
                self.selection = OrderedDict(self.selection + selection_add).items()
    def _description_selection(self, env):