Performance issue when converting PDF to image after upgrading from PDFBox 2.0.20 to 2.0.21

We use PDFBox to save the first page of a PDF as an image to provide a preview of the document. These PDFs can be relatively complex as they may contain ten thousands of objects, especially map data. The results are still fine, but when we upgraded from 2.0.20 to 2.0.21 we had a notable performance decrease. Saving the first page of the attached sample document now takes nearly 20 sec on my developer machine, compared to 4 sec with 2.0.20.