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? https://qa-refapp.openmrs.org/

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.