It looks like ObjectStore doesn't account for the schemas not supported by the Server, i.e. Lists of nullable primitive values are not supported, but Core will happily create the schema anyway (because they are supported for local Realms).

But this then result in a BadChangeset when connecting to the server, which contains a very unhelpful error message.

 ERROR "Bad changeset (UPLOAD)" (error_code=212, try_again=false, recovery_disabled=false)

Ideally, Core should catch this during schema validation and throw an exception. This should be possible since it already knows there that the schema is for a synchronized Realm.