There were 2 issues here contributing:
1. Sentinel was modifying the config options, which we no longer clone. Now, we clone the endpoints and pass them down as explicit overrides into the child connection.
2. EndpointCollection...wasn't actually cloning. I can't believe this didn't show up elsewhere. Collection<T> takes a ref directly without copy of members when forming, so even if ew did clone...we'd be modifying the same thing.