Steps:
1. Put the following command in a command block.
summon MinecartRideable ~ ~1 ~ {Passengers:[

{id:ArmorStand,NoGravity:1,CustomName:V1}

]}
2. Right click the minecart to get inside of it.

Expected Results:
You should be able to get inside the minecart that has an armor stand ridding it.

Actual Results:
In 1.8 you were able to get inside a minecart that has an armor standing ridding it. In 1.9 you are unable to get inside the minecart when an armor stand was riding it even if the armor stand was invisible.

If the intended behavior is that you can't get inside the minecart while something else is riding then can you change this to a feature request? On my server I was able to make cool rides using this set up and would like it back in the base game.