The bug

When a vine hugs a block, and occupies that air-space, you cannot right-click or shift right-click the vines to place another, both on adjacent blocks or "opposite" blocks. This behavior is partially untrue to ladders. Applicable to both Creative and Survival.

How to reproduce

1. Make a 3x3 wall of 9 blocks (so, with a depth of 1)
2. Alligned to the center of the wall, make a 3 block high tower with two spaces of air in between it and the wall.
3. Place vines or a ladder in the center of the 3x3 wall on the side facing the tower. These steps are shown in image.
4. Right-click or shift right-click the faces of collisions on the vine, with a vine, and notice it will not place more despite present blocks allowing it to exist on them.
5. Right-click or shift right-click the faces of collisions on a ladder instead, with a ladder, and notice they will place in all areas except the tower. However, you can place vines off the ladder instead of ladders and they will occupy valid spaces, including the tower.