UE40D6500 Firmware Downgrade from 1026

[ingnaz71]

Hello,
I want to downgrade the firmware from 1026 (the last available up to now) to any previous.
In fact with this release the import/export channel list does not work and also MHP services are not working.
Previous firmwares worked correctly.
I tried the well known procedure to downgrade, by mean of changing the DNS.
Strange think... if after changing DNS I reboot the TV, again appears the automatic connection.
If I do not reboot after changing DNS, the TV will found correctly the FW rev 1090 but the download fails at 95% with error code:0.
I have already tried successfully the downgrade when I bought the TV in order to change regional settings, but now does not work anymore.
Do I have to blame 1026 release???
Any suggestion?
I'm really stuck and don't know how to proceed.
Thanks!

Ignazio