After installing a HAL Validator (https://paragsarin.medium.com/hal-api-validation-754fd3b2c96), and preparing a CURL request, I received the error "0xE2 is an invalid start of a property name". The response of my HAL service validates as JSON already, so why am I getting this error?
Turns out this error was from parsing a json based configuration file of the validator, not the results from validating a HAL response (which is also json). The json in the configuration file turned out to have left and right double quotes (disallowed) rather than standard double quotes. These characters came from copying from a web browser into an editor when creating the configuration file. Swapping left and right with standard double quotes fixed the issue.