Oh gawd. I'm watching the paint dry again. 25 hours in and it's at 64%. Admittedly it's less despair-inducing than when it was at 12 hours and 20%. But it's the worst marathon render I've had to suffer through since DS 3.
Double-sized scene (a diptych), low light and transmapped trees. Bad, bad combination. Plus there is something wrong with the file. I saved multiple copies with different names, once I realized what I was in for. I've have been deleting parts from different ones and rendering the separate elements to build a composite in Photoshop. Most of those rendered in a reasonable time for what they contained. Even the one of just about half of the trees since I'm going to need a layer of those to mask the rest of the elements. That one rendered in just about an hour, no problem. Same lights, same settings. No ground plane to catch shadows, but they were casting shadows on each other. No problem. But now I need the background. I know there's something wrong, because in this one I left one group of figures (about a dozen of them) in, since I needed their shadows, too.
It's a very good thing that I'd already rendered them in a different pass along with some of the special effects. Because in this copy of the file -- which is the same file, just saved with a different name -- the same group of figures have rendered as solid black silhouettes. Apart from about four of the wigs, and a couple of props. The figures, the clothing, the rest of the wigs, most of the hand props. Solid black silhouettes.
This time I know it's a shader issue. No idea how to fix it, and no real need to fix it because I can just plop the other render in over the top. And even if I did fix it, I've no guarantee that it would render any faster.
But, jeez.