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
""" Special value that encapsulates an exception instead of a value. """
    def __init__(self, exception):
        self.exception = exception
    def get(self):
        raise self.exception
def _check_value(value):
    """ Return ``value``, or call its getter if ``value`` is a :class:`SpecialValue`. """
    return value.get() if isinstance(value, SpecialValue) else value
def copy_cache(records, env):
    """ Recursively copy the cache of ``records`` to the environment ``env``. """
    src = records.env
    todo = defaultdict(set)             
    done = defaultdict(set)             
    todo[records._name].update(records._ids)
    while todo:
        model_name = next(iter(todo))
        record_ids = todo.pop(model_name) - done[model_name]
        if not record_ids:
            continue
        done[model_name].update(record_ids)
        for name, field in src[model_name]._fields.items():
            src_cache = src.cache[field]
            dst_cache = env.cache[field]
            for record_id in record_ids:
                if record_id in src_cache:
                    
                    value = dst_cache[record_id] = src_cache[record_id]
                    if field.relational and isinstance(value, tuple):
                        todo[field.comodel_name].update(value)
def first(records):