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
""" Return the current date as seen in the client's timezone in a format
            fit for date fields. This method may be used to compute default
            values.
            :param datetime timestamp: optional datetime value to use instead of
                the current date and time (must be a datetime, regular dates
                can't be converted between timezones.)
            :rtype: str
        """
        today = timestamp or datetime.now()
        context_today = None
        tz_name = record._context.get('tz') or record.env.user.tz
        if tz_name:
            try:
                today_utc = pytz.timezone('UTC').localize(today, is_dst=False)  
                context_today = today_utc.astimezone(pytz.timezone(tz_name))
            except Exception:
                _logger.debug("failed to compute context/client-specific today date, using UTC value for `today`",
                              exc_info=True)
        return (context_today or today).strftime(DATE_FORMAT)
    @staticmethod
    def from_string(value):
        """ Convert an ORM ``value`` into a :class:`date` value. """
        if not value:
            return None
        value = value[:DATE_LENGTH]
        return datetime.strptime(value, DATE_FORMAT).date()
    @staticmethod
    def to_string(value):