There are many community members using these with no issues but I personally removed my two Multisensor 6's from my mesh. They were nothing but problems and like you are observing spammed the zwave mesh. Any device that routed through it was at 9.6 speed too. The final straw for me was documented here.
My advice would be to remove the power and see if things improve and if so you found the issue. I just don't trust the MS6 and swapped mine out with a NYCE ceiling sensor, which unfortunately doesn't seem to be available any longer.
