Two things:
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If the image is wider than the text area, the forum will shrink it to display it. Those shrinked images don't contain the metadata in the original. That's why you sometimes have to show the original image: it happens when the image is wide.
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You have to drag the image into the Scripts tab. If you have the Costumes tab showing, then the image will be imported as a costume (but the metadata is still there, and you can get at it by right-clicking the image). In this case, the image will be displayed in the Costumes tab with a "</>" in the corner to indicate that it contains code.