https://www.odoo.com/forum/Help-1/question/One2Many-Attachment-Field-Download-Error-38407
I'm in Dan's team. I managed to fix this bug by editing /addons/web/controllers/main.py file. Search the saveas_ajax function. Arround the line nr 1307 you will find this:
if filename_field:
fields.append(filename_field)
if data:
res = { field: data }
elif id:
res = Model.read([int(id)], fields, context)[0]edit it to this:
if filename_field:
fields.append(filename_field)
if data:
res = { field: data } # FIX
if filename_field:
filename_name = Model.read([int(id)], [filename_field], context)
res[filename_field] = filename_name and filename_name[0] and filename_name[0][filename_field] or ''
elif id:
res = Model.read([int(id)], fields, context)[0]
