so, im back on the nice n clean image of 4.7.1 but the promlem was still there.
i figured out that was an known issue (i guess) with not saving the system volume.
i fixed it by switching to 3,5mm jack and back to hdmi audio a few times (in all options i found), sometime the volume could be saved.

(i just wrote that to make this thread senseful for some people)

have a nice