Hello EstebanUE4
This error means you are trying to access address that does not exist. This usually occurs when you are trying to access an object that has not been instanciated (created in memory). Or the pointer is not relevant. You say it works when you play in-editor? Maybe you are doing something in construction scripts?
As for debugging version, yes, you have to have IDE with debugging symbols installed at least.
As of now it is just not enough information to resolve your issue.
Regards,
Alex.