File systems /var and /usr refuse to unmount on shutdown

My system, Mageia 6, has 7 file systems (partitions) on the hard drives. They are all mounted as software RAID1 partitions. The file systems are: /, /usr, /boot, /var, /bulk, /tmp, and /home. After I log off, and select "Shutdown" at the initial login screen, I can see the log messages during the shut down, and I observe that /var and /usr fail to unmount. Presumably some application still has one or more files open on these file systems.
Do you have advice on tracking down the cause of these unmount failures?
Do you have advice on tracking down the cause of these unmount failures?
