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
""" Set all field attributes at once (with slot defaults). """
        
        assign = object.__setattr__
        for key, val in self._slots.iteritems():
            assign(self, key, attrs.pop(key, val))
        if attrs:
            assign(self, '_attrs', attrs)
    def __delattr__(self, name):
        """ Remove non-slot field attribute. """
        try:
            del self._attrs[name]
        except KeyError:
            raise AttributeError(name)
    def __str__(self):
        return "%s.%s" % (self.model_name, self.name)
    def __repr__(self):
        return "%s.%s" % (self.model_name, self.name)
    
    #
    
    #
    def setup_base(self, model, name):