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).


""" Return the first record in ``records``, with the same prefetching. """
    return next(iter(records)) if len(records) > 1 else records
def resolve_mro(model, name, predicate):
    """ Return the list of successively overridden values of attribute ``name``
        in mro order on ``model`` that satisfy ``predicate``.
    """
    result = []
    for cls in type(model).__mro__:
        if name in cls.__dict__:
            value = cls.__dict__[name]
            if not predicate(value):
                break
            result.append(value)
    return result
class MetaField(type):
    """ Metaclass for field classes. """
    by_type = {}
    def __new__(meta, name, bases, attrs):
        """ Combine the ``_slots`` dict from parent classes, and determine
        ``__slots__`` for them on the new class.
        """
        base_slots = {}
        for base in reversed(bases):
            base_slots.update(getattr(base, '_slots', ()))
        slots = dict(base_slots)
        slots.update(attrs.get('_slots', ()))
        attrs['__slots__'] = set(slots) - set(base_slots)
        attrs['_slots'] = slots
        return type.__new__(meta, name, bases, attrs)
    def __init__(cls, name, bases, attrs):