runtime/invalid-unbox

This happens when a boxed native pointer is unboxed as the wrong type.

Mitigations

Make sure the cpp/unbox operation uses the same type that was originally boxed. The jank error output should provide you with source information, as well as the expected type for the given box.

Note that opaque boxes always need to store raw pointers. Additional qualifiers like const do matter, when it comes to type comparison. For more information on opaque boxes, see here.