Big thanks to the team at Grommunio for resolving the majority of these issues.
The only one outstanding I believe now is the rogue load_module lines getting added to NGINX. I updated again last night and they got added back in, breaking NGINX once more. Deleting these lines (they're trying to load the modules from the original /usr/share/nginx/modules location but Grommunio moved them to /usr/lib64/nginx/modules) fixes it temporarily, but every time an update gets installs it re-adds the offending lines and breaks NGINX again.
load_module modules/ngx_http_brotli_static_module.so;
load_module modules/ngx_http_brotli_filter_module.so;
load_module modules/ngx_http_vhost_traffic_status_module.so;
