Usually, when a part of the image is missing in the game due to a "blunder" by the developer, an error like this pops up (there are many in this thread):
In your case, I have only three explanations:
1. "Caching is broken" (don't ask what it is) - it can be fixed if you have a previous save file nearby. Restart the game completely and open your previous save file. When you replay this scene, everything will be fine. If the save file is very old, then complete this scene as is, make a new save file and repeat the step from the very beginning - you will not see this bug again.
2. Your
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is "corrupted" (if you installed it at all, as required by the game). Fix:
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it again and reinstall it.
3. In an attempt to "change" Mia clothes, you "disabled" part of the image in RPG Maker VX Ace and are simply "cheating" us all here... There is no cure...