Indirectly resolved. Unfortunately, I am not 100% positive which fix corrected the problem because I was sort of frustrated and trying many things.
I am reasonably confident that ultimately the issue was with my NGINX proxy settings. I was also having unknown errors when uploading some files. Eventually I traced it to nginx and pho post size settings. It seems that once that issue was resolved, the apparent timeout issue went away. I think that there are some ajax calls on the layout designer screen that happened to be sending posts that were too large for nginx.
Sorry that I can’t be sure this is the fix that actually worked, but I would start there.
Jayson