Large Humanoids have a glitchy landed stage, in which they “land” too early and then float down to the actual floor. This bug affects both R15 and R6 as well as custom Humanoids.
It started happening late last year-ish when the Humanoid’s code was updated. I remember seeing a DevForum post about the behavior changes but I can’t find it anymore. I made a bug report in January for this same issue, but I decided to make a better report instead of bumping that one.
This bug has been causing me massive headaches with my sequel to Mashables, a game where a large monster is built by everyone on the server. The monster can be really uncomfortable to control because of this and it’d be really nice if it could get fixed.