I’m not using cpp with my project but there is a similar error you get when modifying structures or array structures in blueprints.
First I’d like to confirm that you’re not trying to use an array structure within an array – the engine seems to have a ton of issues with this.
Moving on: If you make a change to your structure or have try going into every blueprint that uses the structure and save/compile. May fix your issue, here’s to hoping.