I haven't checked on EWA, but it seems they verify all maps included in the collection for correctness. Perhaps the version of Heroes is too far from the original; I've encountered ready-made collections where it was claimed to be version 3.1, but not all functions from 3.1 worked. If the patch was installed manually, there might have been an incompatibility between the game version and the patch version. If you send the save file, there's a chance it will run on my system, and we can more accurately determine the cause of the error. However, in my opinion, it's better to reinstall Heroes from a reliable source and try running it on a "clean" installation.