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
#
        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]
    def _inverse_related(self, records):
        """ Inverse the related field ``self`` on ``records``. """
        
        record_value = {record: record[self.name] for record in records}
        for record in records:
            other, field = self.traverse_related(record)
            if other:
                other[field.name] = record_value[record]
    def _search_related(self, records, operator, value):
        """ Determine the domain to search on field ``self``. """
        return [('.'.join(self.related), operator, value)]
    
    _related_comodel_name = property(attrgetter('comodel_name'))
    _related_string = property(attrgetter('string'))
    _related_help = property(attrgetter('help'))
    _related_readonly = property(attrgetter('readonly'))
    _related_groups = property(attrgetter('groups'))
    _related_group_operator = property(attrgetter('group_operator'))
    @property
    def base_field(self):