We are using TFS 2015 together with the CMMI process template and I have just found out that Issues do appear on the backlog if they are a child of a Feature or a Requirement work item type. If the Issue is standalone (has not link to one of the two mentioned work item types) it is not visible on the backlog.
I guess that someone has made some hacks here in order to make this possible. Originally, only Epics, Features, Requirements, Tasks, and Bugs should appear on the backlog.
I have checked the Issue work item type definition as well as the processconfiguration.xml and the categories.xml which look quite ok from my point of view.
Are there any another places where one could define which work item types should be visible on the backlog?
Thanks a lot for giving support.