When placing Minecarts on a track going up or down or on a curve, you ride in a different position than normal.
What I expected to happen was when I'd put a minecart on a curve, you would ride regularly. Same with placing a minecart on a slanted track.
What actually happened when placing a minecart on a curve was that I was riding on the cart, I was riding unusually, because I was "leaning" on one side of the cart. When placing a minecart on a slanted track, I wasn't riding regularly, because I was sitting at a lower point than normal. Besides that, the cart itself was going below the track as if it was swimming below the tracks, with its top only exposed.
One issue per ticket please, besides that, all of your issues are already reported.