Hi Tom,
No, unfortunately there's no flags or env vars that provide additional detail and information to the log file.
Also, just following up on our request from Friday via our support system, would it be possible for you to render a pass with the trees and ground together; without any holdouts? Basically, a beauty pass of the trees and ground together. We don't necessarily need to see the entire sequence. Ideally, two frames should suffice, where we can see a frame that renders correctly, followed by a frame that has the problem.