SamyGO

If You want to have firmware, compatible with samygo, You have manually flash required partitions via telnet. Its very dangerous, but a lot of people done it w/o problems. Its Your only decision make it or not. For more information look at Wiki. Here is manual how to flash Your backup partitions with earlier version of firmware and add right identifiers to activate alternative fw menu. You don't have enter exact commands as is shown, adopt it for Your TV at first.
Enable telnet with Samygo Trojan Horse.

Another topic about rolling-back. But here You just read about. Info on wiki is simplification of the way discussed on that topic. Ask before doing if You don't understand, because You can easily brick TV. I would recommend before You do that tricks - enter to Service Menu and enable ExLink cable debug mode (probably it doesn`t work at all, because flashing of the latest firmware deletes some code from TV, but if it works, it helps to repair TV in case You brick It.)

Pls write full TV model and firmware version, because if TV is CI+ it`s more dangerous and the instruction to flash is a little other as in case TV is CI.

Now you can use new samygo application to roll-back.
i think it`s time to move info to wiki...

I thought, here is detailed enough to use it...
Read this post and posts below, you find all answers. If you dont, write and i`ll help.