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
comodel = records.env[self.comodel_name]
        
        
        domain = self.domain if isinstance(self.domain, list) else []
        wquery = comodel._where_calc(domain)
        comodel._apply_ir_rules(wquery, 'read')
        order_by = comodel._generate_order_by(None, wquery)
        from_c, where_c, where_params = wquery.get_sql()
        query = """ SELECT {rel}.{id1}, {rel}.{id2} FROM {rel}, {from_c}
                    WHERE {where_c} AND {rel}.{id1} IN %s AND {rel}.{id2} = {tbl}.id
                    {order_by} {limit} OFFSET {offset}
                """.format(rel=self.relation, id1=self.column1, id2=self.column2,
                           tbl=comodel._table, from_c=from_c, where_c=where_c or '1=1',
                           limit=(' LIMIT %d' % self.limit) if self.limit else '',
                           offset=0, order_by=order_by)
        where_params.append(tuple(records.ids))
        
        group = defaultdict(list)
        records._cr.execute(query, where_params)
        for row in records._cr.fetchall():
            group[row[0]].append(row[1])
        
        for record in records:
            record._cache[self.name] = tuple(group[record.id])
    def write(self, records, value):
        cr = records._cr
        comodel = records.env[self.comodel_name]
        parts = dict(rel=self.relation, id1=self.column1, id2=self.column2)
        def link(ids):