Apparently... Crew was making an visual appr, put gear down and at some point they get a LG Lever Disagree. EICAS and RMU both show 3 greens. Crew touches down, hears a big clunk (1 of the main gear collapsing?), initiate go-around, do a fly-by and confirms 1 of the mains isnt fully down. They cant get it to extend, so they retract gear and bring it in on the belly. MX got the plane into the hangar and repeated the problem with the same results. The whole crew was very experienced and did a great job, pax deplaned with no injuries.