MC-38490 is not resolved.
Dismounting a minecart in an open field will teleport you to 3 metres in x and 3 metres in z direction, instead of on top of the cart, as it used to be before 1.7.
When there is a wall in between, you may move through the wall as well.
When it is in the air, you will fall down from that point to ground, water, lava.
This is also the cause of MC-37365, probably.
My guess: the dismount function looks for an open space in a 7x7 raster centered around the minecart. It starts looking in the far corner, and if that is available, then that is where you go.
IM(v)HO: Dismount should be on top of the minecart, but not in it, or if there is not enough space, the landing should be in the open space nearest to the minecart.
MC-38490 is resovled because it is a duplicate as is your report. If you have not , please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.