This is the expected behavior. It is not allowed to click on button from a children record (e.g. inside a One2Many) if it has been modified.
Indeed you should not work on invoices nor shipment from the One2Many but from the relate. I think we should remove the form mode of those One2Many to avoid such astonishing. So I change the issue into a feature request.
|2018-10-27 14:27:09||ced||set||messageid: <firstname.lastname@example.org>|
|2018-10-27 14:27:09||ced||link||issue7823 messages|