Found this posted on the FB page of a fairly respected aviation author:
Polish 767 belly landing may have been caused by a tripped alternate gear extension CB not known of by the pilots or even the airline.
I heard this through the grapevine. LOT had a low center hyd message after takeoff. They turned off the center system for the flight, but quantity was too low to get the gear down on arrival. The alt gear extension in the 767 is an electric motor that unlatches the gear up-locks. They tried the switch to no avail. Later, post-crash, they found an alt gear cb tripped. Neither the crew nor the airline new about the cb and there is no EICAS message for this cb. My books don't show the CB but my 767 books are way out of date.