Edit: Duplicate of MC-158169, I didn't see because it wasn't marked for 1.17 or the pre-release

When a minecart drives over a slope and there is another rail under the block the slope goes up to (see attachments), the minecart will visually teleport to the rail underneath the block. The hitbox does not teleport with it. This happens both when the rail underneath is a corner pointing into the block under the slope and when it's straight.