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).


'_attrs': EMPTY_DICT,           
        '_module': None,                
        '_setup_done': None,            
        'automatic': False,             
        'inherited': False,             
        'name': None,                   
        'model_name': None,             
        'comodel_name': None,           
        'store': True,                  
        'index': False,                 
        'manual': False,                
        'copy': True,                   
        'depends': (),                  
        'recursive': False,             
        'compute': None,                
        'compute_sudo': False,          
        'inverse': None,                
        'search': None,                 
        'related': None,                
        'related_sudo': True,           
        'company_dependent': False,     
        'sparse': None,                 
        'default': None,                
        'string': None,                 
        'help': None,                   
        'readonly': False,              
        'required': False,              
        'states': None,                 
        'groups': None,                 
        'change_default': False,