My browser is told by Orion to request the following URL: localhost:17779/.../render
Is this expected?
To be clear, this is the format of the URL even when accessing it from a remote machine.
that looks like the Engineers Toolset plugin is being polled for info...
Yep, exactly that. If you don't have toolset installed on your machine, you can turn off the toolset integration in your user account in Orion.