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).


""" set the value of field ``self`` on ``record`` """
        env = record.env
        
        record.ensure_one()
        
        value = self.convert_to_cache(value, record)
        if env.in_draft or not record.id:
            
            spec = self.modified_draft(record)
            
            env.cache[self][record.id] = value
            if env.in_onchange:
                for invf in record._field_inverses[self]:
                    invf._update(record[self.name], record)
                env.dirty[record].add(self.name)
            
            if self.relational:
                spec += self.modified_draft(record)
            env.invalidate(spec)
        else:
            
            write_value = self.convert_to_write(self.convert_to_record(value, record), record)
            record.write({self.name: write_value})
            
            if not (self.relational and not all(value)):