No, it runs fine and also works from all of the IOS devices that use the 2.1 SDK(exact same code).
My code is nearly identical to the GPSync sample too, just passing a single point as a feature set and a linear unit.
Only difference is the new SDK is 2.2.1
Any code snippets for me to inspect all of the input parameters as JSON(how can I see the entire request as JSON)? the error appears to be a JSON string issue?