Reset functionality is not working on Fill heightmap Using Neighbours

Steps to reproduce:

1. Create a new Project
2. Create a Terrain Object
3. Select Terrain Object > Inspector > Terrain > Create Neighbour Terrain
4. Select Fill Heightmap Using Neighbours
5. Click on cogwheel and click on Reset

Actual Result: Value is not set to default

Expected Result: Value set to default

Environment:
Mac 10.14 and Windows 10

Reprodicible on
19.3.0a2, 19.3.0a1, 19.2.0a14, 19.1.0f2