Web Services with Custom Extension

We  have been working on a custom Druid extension for our processes and everything works in Studio and when run on a Job Agent in RapidMiner Server. However, if we expose a process as a Web Service, it fails to find some classes. The jar for the extension includes the classes in question, so it seems pretty odd. We can see logs where the code for the extension is executing so it is getting that far at least. We also tried dropping a jar in the libs that resolves this class, but it still doesn't find it.