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
""" Very similar to :class:`~.Char` but used for longer contents, does not
    have a size and usually displayed as a multiline text box.
    :param translate: enable the translation of the field's values; use
        ``translate=True`` to translate field values as a whole; ``translate``
        may also be a callable such that ``translate(callback, value)``
        translates ``value`` by using ``callback(term)`` to retrieve the
        translation of terms.
    """
    type = 'text'
    column_type = ('text', 'text')
    def convert_to_cache(self, value, record, validate=True):
        if value is None or value is False:
            return False
        return ustr(value)
class Html(_String):
    type = 'html'
    column_type = ('text', 'text')
    _slots = {
        'sanitize': True,               
        'sanitize_tags': True,          
        'sanitize_attributes': True,    
        'sanitize_style': False,        
        'strip_style': False,           
        'strip_classes': False,         
    }
    def _setup_attrs(self, model, name):