Cannot paint over terrain layers?

I am using Unity 2018.3 and downloaded the new terrain tools as per the blog. In a new project, I imported a couple of texture packs and https://assetstore.unity.com/packages/3d/environments/landscapes/free-island-collection-104753 to use as a terrain base. Everything imported fine and I noticed that painting the terrain now uses terrain layers.

My problem is that I cannot seem to paint over a layer with an existing (from _TerrainAutoUpgrade) or if I add a new layer. If I try to paint over one of the layers, it makes changes to a greyish shade instead of the new texture. Is it because of the terrain being imported with textures? If I create a brand new terrain it seems to be ok, except if trying to paint with the first texture over a subsequent colour. Then the same grey painting happens.

Attached an image where I tried to paint black over exiting terrain layers to show what happens.

 

This is beginning to look like I will have to delete all the imported terrain textures and paint from scratch. After more testing, I created a brand new project without the the new terrain tools (base 2018.3) and imported the free island pack again. The imported textures convert to terrain layers, but if I try paint over anything with one of the existing layers, the above problem occurs. I also get "Graphics.CopyTexture called with mismatching mip counts (src 12 dst 1) UnityEngine.GUIUtility: ProcessEvent(Int32, IntPtr)" in the console. If I create a brand new layer I can paint. If I replace an existing, I cannot. If I delete all the terrain layers and start fresh, I can paint.

Is this going to be an issue for any older terrain assets being imported?

 

that's because only 8 textures support by terrain for now. Reduce texture count

 

* facepalms *
Thank you

 

I tried everything, I can only set the base layer. Any other layer is not painted.

 

Same issue here. Each time I try to paint on a base layer I get:
OPENGL: Graphics.CopyTexture called on textures of different sizes?
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

OPENGL: Graphics.CopyTexture called on textures with different mip count (10 vs 9)?UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

P.S. When I do the same actions in an empty project it does work, perfectly. However, I still can't figure out what could I break in the original project to get above mistakes.

 

The solution (for some reasons) is to set, in quality settings, Texture Quality to full res

 

I was having a hard time figuring out why i couldn't paint my terrain.
elettrozero's solution worked for me.
Thanks!

 

Wow. This was a lifesaver for me. Thank you. Had the same problem, this fixed it for me. This should be in a FAQ or something.

 

elettrozero's solution worked for me.

 

elettrozero's solution saved me

 

elettrozero thank you so much problem solved

 

not worked for my case, I am using 2018.4.5