You can try to downgrade your MAG256 to the imageupdate 2.20.03:
Download this file
https://www7.zippyshare.com/v/zsLdVQag/file.html
and save it on a USB stick in a folder called mag256.
Before you downgrade, don't forget to disable automatic update in the Embedded Portal:
1. Load Embedded Portal
2. Select Settings
3. Select Software autoupdate
4. In Autoupdate select "Disabled"
5. Press OK to save the changes.
Downgrade imageupdate:
1. Connect prepared USB-drive to STB.
2. Then enter the System Recovery Utility menu:
a. Power off STB (unplug the power supply).
b. Push and hold Menu button on RC and power STB on (still holding Menu button, plug in power supply).
c. Wait for ~10 seconds ⇒ System Recovery Utility menu.
Release Menu button.
Note: the Menu button on the RC is located on the left hand side below the down button and above the Vol+ button. The one with the 3 lines and 3 dots.
3. Select Upgrade Tools ⇒ Upgrade Software ⇒ Using USB ⇒ Yes; and select your file.
4. Wait until the update process is complete. The info about software update status is displayed at the bottom of screen.
When the software is updated the STB will automatically reboot.
Good luck