Rendering of vector object is different in Acrobat

Hello, I just noticed that the PDF displays the drop shadow as a flat rectangle in Acrobat.

Compared to other previews (Apple or Foxit PDF Reader), this currently only seems to occur in Acrobat.

Does this have anything to do with the Adobe PDF Library which is used in Acrobat for rendering?

The file was reduced to the objects causing the problem.

According to the document info, the original file was previously created in InDesign.