Ver no log do sistema se há seguidos erros no acesso de arquivos:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/addons/base/models/ir_attachment.py", line 113, in _file_read
    r = base64.b64encode(open(full_path,'rb').read())
PermissionError: [Errno 13] Permission denied: '/var/lib/odoo/filestore/xxx/17/175fcdfd38bac59b84f2765c79437cc971e27569'
2022-05-05 18:22:01,499 3580 INFO xxx werkzeug: 172.71.10.62 - - [05/May/2022 18:22:01] "GET /web/content/319-e57268f/web_editor.assets_editor.0.css HTTP/1.1" 200 - 4 0.011 0.017
2022-05-05 18:22:01,505 3580 INFO xxx odoo.addons.base.models.ir_attachment: _read_file reading /var/lib/odoo/filestore/xxx/8d/8d03406676ca42bb1f6923accb0bc1f53fbef227 
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/odoo/api.py", line 1049, in get
    value = self._data[key][field][record._ids[0]]
KeyError: 479

confira as permissoes do repossitorio : sudo ls -l /var/lib/odoo/filestore
total 5652
drwxr-xr-x 238 odoo odoo    4096 Oct 20  2021 aaaaaaaaaaa
-rw-r--r--   1 odoo odoo 2009252 Jun 25  2021 bbbbbbbbbbb
drw------- 197 odoo odoo    4096 May  3 13:32 xxx
drwxr-xr-x 174 odoo odoo    4096 Jun 18  2020 ccccccccccc
drwxr-xr-x 186 odoo odoo    4096 May 26  2020 ddddddddddd

atribua novas propriedades de leitura/gracao/remocao a todos os grupos de usuarios:
 sudo chmod -R 777  /var/lib/odoo/filestore/*