My company has used InfoPath 2013 to create a form to allow external users to submit issues into a List in SharePoint online. Local domain users (those with company e-mail credentials) can view, submit, edit and otherwise use the InfoPath form without problem.
Those external to the company (our clients), even though they have all the necessary permissions in the SharePoint (Contribute Level) get a permissions denied error when creating a new item on the list or editing an item.
The truly strange thing is, that even though they receive the error, the new item or the edits to the existing item is saved anyway.
My client is extremely frustrated by this, and I have been unable to figure out this problem over the last month. Any and all suggestions would be welcome.