after i got the haedphone back from the first repair i tried testing it for a longer time.
when the 009 looses the right channel as a result of hearing a lot of music, the headphone recovers slowly after a week not using it.
why this happens--i dont know.
then i started a new stresstest to see how it will develop and let it rest for a week again.
as i was 100% shure that the 009 will always behave the same way, we send it in for a new repair-service.
but inbetween i got my new motorcycle and a longer vacation and, and ..... so it took some time.
in fact, the second service ended with a new headphone but no comment from the repaircenter.
for now everything seems to be ok. 15 hours of burn-in and no imbalance occurred.