I have been running into an issue where creating a new MatPBRBasicGlass material, or duplicating from an existing MatPBRBasicGlass, breaks and appears to possibly drop the texture resolution down to such a low amount, it appears as if there is no texture. Everything works fine until you close the Material window for the first time after creation/setup. Opening the Material window again, doesn't seem to fix the issue, and when in game, the issue persists. Only creation of a new Material, will seem to fix it temporarily until you close that material again.