Creating and updating textures from Blueprint

I am trying to save a render target into a texture in the content explorer to render icons for items.

I am using RenderTargetCreateStaticTextureEditorOnly to create them and ConvertRenderTargetToTexture2DEditorOnly to update them.
Everything seems to work fine, although saving is dodgy every now and then because some times it can’t save and I have to restart the engine.
Here you can see the Blueprint nodes: Render To Texture posted by anonymous | blueprintUE | PasteBin For Unreal Engine 4

The problem now is when I build the game I get
UATHelper: Packaging (Windows (64-bit)): LogAssetManager: Error: Registered PrimaryAssetId Icons:T_Icon1 for asset /Game/Blueprints/GenerateIcons/Icons/T_Icon1.T_Icon1 does not match object’s real id of ! This will not load properly at runtime!

The textures id seems to be null. What is the right way of doing this?

I already added the folder path as a primary asset path to the project settings.