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).


record._prefetch_field(self)
        elif self.compute:
            
            
            if self.recursive:
                self.compute_value(record)
            else:
                recs = record._in_cache_without(self)
                recs = recs.with_prefetch(record._prefetch)
                self.compute_value(recs)
        else:
            
            record._cache[self] = self.convert_to_cache(False, record, validate=False)
    def determine_draft_value(self, record):
        """ Determine the value of ``self`` for the given draft ``record``. """
        if self.compute:
            fields = record._field_computed[self]
            with record.env.protecting(fields, record):
                self._compute_value(record)
        else:
            null = self.convert_to_cache(False, record, validate=False)
            record._cache[self] = SpecialValue(null)
    def determine_inverse(self, records):
        """ Given the value of ``self`` on ``records``, inverse the computation. """
        if isinstance(self.inverse, basestring):
            getattr(records, self.inverse)()
        else:
            self.inverse(records)
    def determine_domain(self, records, operator, value):