So I was creating a minecart system to get around my mines and my house and it was working successfully until I used rode my minecart from around bedrock level to the surface. I expected to have a clean ride, but instead, at around maybe y=30 (rough estimate), as the minecart went uphill on the tracks, it suddenly started going back downhill, as if it hit something at that y=30 height level. I checked to see if the same happened when the minecart was initially going downhill, but the minecart continued to move unaltered. I went into creative mode and the same thing happened at the same height.

Steps to Reproduce:
1. Mine in a step pattern down to bedrock.
2. Lay down all powered rails (or just enough to go uphill successfully) throughout the whole tunnel.
3. Get in a minecart at the bottom and ride up the tracks.