How to reproduce:
1. Create a new project
2. Create a terrain (right-click in Hierarchy tab -> 3D Object -> Terrain)
3. Click on 'Paint Details' button in the Inspector
4. Click on 'Edit Details...' button -> 'Add Grass Texture'
5. Select any sprite in 'Detail Texture field' (ex. 'Knob') and press 'Add' button
6. Make sure that Target Strength equals 1
7. Select created grass texture and paint the terrain

Expected result: Grass textures placed next to each other
Actual result: Big spacing between near grass textures

Reproducible: 2019.1.4f1, 2019.2.0b4, 2019.3.0a4
Not reproducible: 2017.4.28f1, 2018.4.1f1, 2019.1.0a1, 2019.1.0b1, 2019.2.0a1

Notes:
- Workaround: Create terrain with older version project where the issue is not reproducible and update project