Hi,
You can go to the following path:
/All/EngineData/Plugins/MetaHumanCharacter/BuildPipeline
There, you’ll find a file called BP_DefaultLegacyPipeline, which contains some settings used during the build process of your MetaHuman.
Next, check the texture graph instance that includes the TGI_Skin_sRGB asset. From what I understand, this graph defines certain rules used to bake the textures.
The issue is that by default, only the Base Color texture is set to 2K resolution. Changing it to 8K should resolve your issue.
Good luck!