Steps to reproduce:
1) Open the project attached by me.
2) Build the project for iOS.
3) Deploy the project to a device via Xcode.
4) Open the app.

An object is being serialised into JSON and then converted back. The lower panel shows which attributes can be written to (CanWrite) or the JSON string, the 'INFO' button can be used to switch between the two. Pressing the 'UPDATE' button re-serialises the object and increments the 'count' value.

In the Editor, all the attribute values are 'True', that means that they can be written to. However, if the project is deployed to iOS, using IL2cpp, the values of 'Attributes' and 'Metrics' are false. This issue is not present with Mono2x.