If a minecart intersects with a piston head and you power the piston, it will be pushed forward in all directions, except east, it will not move and be pushed backwards when the piston de-powers.

To recreate: place a piston down with a single glass pane on top, let a minecart clip in to the piston with a sloped rail and power the piston. The minecart should be pushed forward in every direction, except when the piston is facing east. When you depower the pistons, every minecart stays in place except one clipped in to the east facing piston, that one snaps back.

Versions:

In 1.9 this became possible due to glass panes not being counted as a full block anymore, and when the piston got powered, a minecart would be pushed over 2 blocks. This was possible in every direction.
In 1.11, the behavior for minecarts intersecting with piston bolts changed to move the minecarts one block over, in stead of two, but minecarts still got moved in every direction.
In 1.13, minecarts get moved back one block in the east direction.

Edits:

In version 1.18, 1.18.1 and 1.18.2 this bug is fixed, every minecart is now working the same in every direction without snapping back