Slow Shutdown after CAVL installation on Mint LXDE 18

since some weeks i am using unofficial german version of Linux Mint 18 LXDE 32 bit on my Dell Mini 1011 (10v).
so far everything works fine and fast.
now i (after successfully installing CAVL with LM 18 Xfce 32 bit and LM 18 Cinnamon 32 Bit) gave it a try with CAVL 32 bit and LXDE.
the .deb file was successfully installed with gdebi (all dependencies available and installed) and after a restart CAVL could be updated and runs with KINTAs patch for kernel >3.2.
only one problem appears, which i never knew on older Linux Mint versions. when CAVL is running and system is shut-down, it takes about 2 minutes to switch off.
before CAVL was installed shut-down is completed in about 5-10 seconds. i tried to close CAVL before shutting down the system and it works fast again (5-10 seconds).
so, something depending on CAVL causes a shut-down delay of nearly 2 minutes.
by the way when i just do a restart, or do a hibernation to disk and resume there is no delay - it is just when system has to be fully shut down.
any suggestions how to solve that?!