Server: Debian 3.2.73-2+deb7u3 x86_64
java version "1.7.0_101"
OpenJDK Runtime Environment (IcedTea 2.6.6) (7u101-2.6.6-2~deb7u1)
OpenJDK 64-Bit Server VM (build 24.95-b01, mixed mode)
Jenkins ver. 2.7.1
Priority Sorter ver 3.4
When you rename a job group that is set to "Jobs marked for inclusion", all the jobs that were marked as belonging to that group lose their assigned group.
I think this is because job group membership is stored by name in the config.xml, rather than by a unique ID, so if the name changes the job is set to be a member of a non-existent group.