Need Help with D6530WS firmware downgrade

[SkiMan5]

Hi,
could somebody help me to downgrade UE40D6530WS with 001027 firmware. I've gone through the topic of downgrading firmware on D-series (all 21 pages), tried everything, different dns(149.154.159.183, 46.4.199.222, 178.62.149.40) both on TV and on modem, factory resets. Every time I got 601 error...
It drives me crazy, as the last update of firmware to 1021 dumbed the TV, it cannot install apps and etc.

Is there any way to downgrade, or I did something wrong? I'm lost, as i did try everything in the topic.

Thank you in advance,
Slava