Upgraded successfully my device RB951G-2HnD to 6.17.
After restart (maybe second) multicast package disappeared from installed packages, and my TV stopped to work 
Connected to device, copied package manually one more time, restarted, all went OK, but again, after power loss package disappeared again from installed packages.
Installed manually again, very strange. Before that, never had similar problems.
make one backup generating one .rsc file (“/export file=bakup”)
savfe the file somewhere
use netinstall and install without keeping previous config routeros-mipsbe-6.17.npk and multicast-mipsbe-6.17.npk
restore (by winbox opening mac address) on new terminal
section by section (for see if are present some errors)
the file previously saved,
untill you not paste back all the file.
REMEMBER TO UPGRADE THE BIOS! on system/routerboard