unable to umount /tmp

since last update to 2.1.25 yesterday i've got problems to shutdown/reboot the system.
the system is unable to umount /tmp ... "device is busy"

but fuser -m /tmp shows three services
3 x twonky
1 x mysql

all of them are closed while shutdown.
also by manually stopping them before initiating a shutdown manually this error occurs.

system hangs complete
only way is hard power off

found no working solution for this problem

hopefully anyone has an helpful idea

regards

Rico

Server is a HP gen7 N40L
OMV is installed on a SSD (64GB)
The data store is a SnapRaid ( 2x2TB data, 1x2TB parity)

problem was caused by errors in AUFS ... see --> HERE <--

solved for now