I have had the issues and this morning received the following response,
i am sorry for the long waiting, we planned to have some stock in the mid of January, however, we noticed there were many customers saying they had the one side problem. Therefore, we have got some defective items back for further investigation and found out the root cause. The main reason we found that the earbuds filter was filled out of some kind of oil stucking the filter to cut down the sound. We are now changing the structure of the filter inside now, it may takes 4 weeks, is that okay you give us more time to get an upgraded version?