Response 500 Error in API Documentation

Hi, all! I have been working on a webservices REST module ticket 843 recently ([RESTWS-843] Wrong Spelling for Appointment-Scheduling Response Pay Load Message - OpenMRS Issues), which has required me to run the Standalone Reference Application 2.12.2 to replicate the bug. I have done this successfully, but when I execute the code from the ticket into the API Documentation, I get a 500 Error: Internal Server Error. Attached are screenshots to the API Documentation found from System Administration > REST Web Services > API Documentation in the Standalone App, which is where I POST the call. Can you spot any mistakes on my part, which may be causing this error?

Are you able to reproduce it on this server?

Thank you for the suggestion! When running it on that server, I now receive a NetworkError instead of a 500 Error.

Also, at the top of the page when it is first loaded, I see this error, which I am not sure how to approach.

Which version of OpenMRS are you running?

I am running this on OpenMRS Standalone App 2.12.2.

Do you have any local modifications to any of the modules?

No, I do not.

Update to the latest snapshot version of the restwebservices module and tell me if you still get the same error.