I was having this problem and couldn’t find any way to clear the VRAM on the forums, so I started messing around with the Daz3D settings and found an easy way to do it without restarting Daz3D. It’s actually very simple and practical: in the Render Settings options, next to Editor, there’s a tab called Hardware. Just uncheck the GPU and then check it again, and Daz will instantly clear the VRAM. Do this after rendering and it will free up the memory without needing to restart Daz. This was the only solution I found.