The brush is tiling when it's size is reduced

Steps to Repro:
1. Open attached or create a new project
2. Hierarchy > right click
3. 3D object > terrain
4. Select raise lower terrain from paint tab
5. Set brush size to 10
6. Move cursor above the terrain

Actual Result:
Observe that brush is tiling

Occurring with:
2018.3.0a6, 2018.3.0a5, 2018.3.0a4

Note:
New Terrain tools are introduced from alpha 4

Working with:
2018.2.0f2

Environment:
Windows and Mac