The dismount radius for boats, minecarts and horses is too big. Has it been enlarged? Example: when riding a horse into a stable and clicking Left-Shift, it now frequently happens that the players lands outside of the walls of that stable. Similarly, when dismounting a minecart, it is now possible for the player to land outside the station.
I have fallen into lava 5 times because of this glitch. It is especially a problem when dismounting to let a horse go through a portal in the nether. Even if the portal in enclosed in a room made of cobblestone (2X4X3 inside dimensions with 3 walls) when dismounting it is common to be booted out of it and to fall into lava.