Screenshots fail to display in Flathub page for net.sourceforge.pdfchain app

[nbenitez]

I initially reported this bug to Flathub website component, but was told there that this is really an appstream bug, so I'm filing it here too.

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I'm the maintainer of https://flathub.org/apps/net.sourceforge.pdfchain and I just noticed that although the app has 6 different screenshots, the webpage only displays one screenshot but repeated 6 times.

I presume the bug is related to the fact that screenshots have same name although their paths are different. They are different URI's so I think they should be permitted like that.