This helped!
Fresh Windows 10 installation and all 7 GPUs able to run even without 6xGPU MOD! I can't believe how much time I lost trying to get 5+ GPUs to run on Windows 7...

Thank you batko and lbr for help!

Now I "just" need to resolve stability issue of 6th and 7th GPU, which crash always after 5-6 minutes of mining.