Problem with images when converting PDF to PDF/A

Hi,

in my PDF file I have some images in PDF-Format that I cut with Adobe Acrobat before using them in the document (created with Latex). Now, I need to convert my PDF to PDF/A but when I do the conversion using Adobe Acrobat the images are not displayed properly. See attached images.

Any idea what goes wrong or how to convert the document properly?

Thanks,

Dennis

Original:

Image may be NSFW.
Clik here to view.

After conversion to PDF/A:

Image may be NSFW.
Clik here to view.