It's a strange issue. Sometimes we see problems with DR nodes which cannot load proxies (bad network paths and so), but not that render different.
Is there some change turning on Render Settings->Distributed Rendering->Transfer missing assets ?
Anyway, there is not any benefit using proxies in RailClone. We included them just for compatibility, but internally all segments are converted to native V-Ray instances.
If that solves the problem, i suggest you use the mesh object directly.