Suppose that we have a form view with a one2many field o2m_1, displayed as a list. The model of o2m_1 contains a one2many field o2m_2 which isn't displayed in the list view, but which is in the form view. If an onchange sets the value of o2m_1, e.g. with a command 0 to create a new record, and that the value of o2m_2 for this new record is set (e.g. with a command 0 as well), it crashed.