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.browse(act[1]).unlink()
                elif act[0] == 3:
                    inverse_field = comodel._fields[inverse]
                    if inverse_field.ondelete == 'cascade':
                        comodel.browse(act[1]).unlink()
                    else:
                        comodel.browse(act[1]).write({inverse: False})
                elif act[0] == 4:
                    record = records[-1]
                    line = comodel.browse(act[1])
                    line_sudo = line.sudo().with_context(prefetch_fields=False)
                    if int(line_sudo[inverse]) != record.id:
                        line.write({inverse: record.id})
                elif act[0] == 5:
                    domain = self.domain(records) if callable(self.domain) else self.domain
                    domain = domain + [(inverse, 'in', records.ids)]
                    inverse_field = comodel._fields[inverse]
                    if inverse_field.ondelete == 'cascade':
                        comodel.search(domain).unlink()
                    else:
                        comodel.search(domain).write({inverse: False})
                elif act[0] == 6:
                    record = records[-1]
                    comodel.browse(act[2]).write({inverse: record.id})
                    domain = self.domain(records) if callable(self.domain) else self.domain
                    domain = domain + [(inverse, 'in', records.ids), ('id', 'not in', act[2] or [0])]
                    inverse_field = comodel._fields[inverse]
                    if inverse_field.ondelete == 'cascade':
                        comodel.search(domain).unlink()
                    else: