Today I'll explain the Iray Texture Compression and how to adjust/disable it. It's a feature that's trying to save you some VRAM at the expense of compression artefacts akin to JPEG images. Up until Daz Studio 4.22 those settings could not be saved and would reset after a restart, but in the latest Beta version 4.22.1 (and later releases) these settings are moving to a different location and can be saved as part of your scene or a Render Settings Preset.
Enjoy, experiment and tell other users about this!