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).


super(_Relational, self)._setup_regular_base(model)
        if self.comodel_name not in model.pool:
            _logger.warning("Field %s with unknown comodel_name %r", self, self.comodel_name)
            self.comodel_name = '_unknown'
    @property
    def _related_domain(self):
        if callable(self.domain):
            
            return lambda recs: self.domain(recs.env[self.model_name])
        else:
            
            return self.domain
    _related_context = property(attrgetter('context'))
    _description_relation = property(attrgetter('comodel_name'))
    _description_context = property(attrgetter('context'))
    def _description_domain(self, env):
        return self.domain(env[self.model_name]) if callable(self.domain) else self.domain
    def null(self, record):
        return record.env[self.comodel_name]
    def modified(self, records):
        
        
        
        spec = super(_Relational, self).modified(records)
        for invf in records._field_inverses[self]:
            spec.append((invf, None))
        return spec
class Many2one(_Relational):