I have now also WhatsApp contact with Toolkitrc..., but somehow they don't seem to really know what the problem could be. They have lots of tips, but I've already tried them all. Otherwise I'm really happy with the M8D, I also did a "comparison" with my Junsi 406, fully charged two 2S LiPos from storage, with the same charging power, apart from 2 minutes both chargers were equally fast and well balanced. Since my Junsi was calibrated by a specialist, I was also able to determine that the M8D was always showing 0.02V per cell less and less, I fixed this by adjusting the M8D.
Then the same thing again, i.e. charged the LiPos, see, the voltages are exactly the same from the Junis 406 to the Toolkitrc M8D. So my Junsi will stay at home in the hobby cellar in the future and the M8D will accompany me to the races....