TerrainEditor Reaname Alphamap program issue?

I tried several times to rename the alphamap of my terrain(s).

Has anyone ever used/tried this option? Cause it seems its somehow bugged.

Kind regards
Alex

It seems that I have to delete and completely rebuild my prebuilded scene now.

Infact its not clear to me what this rename failure did to the scene. I tried to fix the scene but it is still broken.