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Downloaded maps, as well as those you create in the editor, are most likely located in the same Maps folder. This means that they have the same path. Most likely, your path contains characters that are not in the Latin alphabet, for example: D: мои игры: герои 5: HOMM_V: Maps: Karta1.h5m
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True, I'm not sure, but I read somewhere that the problem might be in this.