Steps to reproduce:
1. Open QA's attached project
2. Open scene "Repro"
3. Move the "Player Sprite" along the walls
4. Notice how with Custom Axis set to X=0, Y=1, Z=0 the sprite appears behind only above the center of the Tilemap

Expected result: Center of the Tilemap does not affect the Custom Transparency Axis
Actual result: Center of the Tilemap makes Custom Transparency Axis hide sprites only to a specific direction from it

Reproduced with: 2017.2.0a4, 2017.2.0p3, 2017.3.0b11, 2018.1.0a5

Note: Tilemaps introduced in 2017.2.0a3, hence reproduced only with these versions