Not a real problem but a bug report (I already searched for it and it was resolved due to a 3rd party lens mounted, but that's not the case with my problem): The battery will in some cases drain approx. 5% while the camera is switched off.
So everything started when I upgraded my 6D to the latest nightly for firmware 1.1.6 (2017may7). Within 2 days 2 different batteries (original and copies) got completely drained over night (also with different lenses attached), I think the camera was off but I'm not sure. On the 3rd day I had a shoot, so on the morning I charged a battery and put it in (Pretty sure that the camera was off). After 5-6 hours when the model arrived, battery was dead and cam wouldn't start.
So in the evening I tried to narrow down the problem. - Used a different SD or hold Set-Button so ML wouldn't load. Battery gets not drained. - Used the ML SD again, battery drained from 90% to 80% in about half an hour.
After testing with used modules OFF and ON again I noticed the drain problem seemed not to be there anymore. I initially had the following plugins turned on: ettr, dual_iso, mlv_rec, mlv_snd, silent. Whats even stranger, instead of 80%, today it would show me 90%. (maybe battery estimation is a little unreliable?)