Can't update thumbnail of Texture 2D Array asset when upate source texture resource.

Texture2DArray asset thumbnails are not reflected when the source file texture is changed. Once a Texture2DArray asset is opened and loaded, the thumbnail will follow any subsequent source file updates. 

1. Open the attched project in editor.
2. Open texture "T_sources_B".
3. Change source file and reimport in texture.

Result: 

Update "T_sources_B" asset thumbnail.

Expected:

Update "T_sources_B" and "TA_sources" asset thumbnail. 

("TA_sources" is Texture 2D Array asset which is referenced to "T_sources_B" asset)