to be honest, I think it might be trying to use that by default, but I will try your new image, thanks for the speedy fix!
Well since was RVZ was introduced last year Add support for the WIA and RVZ disc image formats by JosJuice · Pull Request #8538 · dolphin-emu/dolphin · GitHub I guess you've compressed your images lately? Because I use GCZ as format and had never a single problem to load any game. Anyway it should be fixed, at least I've recompressed an image & it works now.