Grey-ish balls below and beside title box in beamer presentation

Question

I have successfully used beamer for many a presentation, but there is a small blemish that I would like to resolve/fix. When I use theme Boadilla and color theme crane, on my title page, at the bottom left and the top right the orange frame surrounding the title, there are small grayish circles (gradient color, half sitting 'under' the orange frame). These are ugly!

How do I make them go away? What causes them to begin with?

Edit: add minimal reproducible example.

\documentclass{beamer}

\usetheme{Boadilla}
\usecolortheme{crane}

\title[CS/SE 2S03]{Principles of Programming}

\begin{document}
\begin{frame}
\titlepage
\end{frame}
\end{document}

Edit 2: as per the answer linked to below, I tried

\setbeamertemplate{blocks}[rounded][shadow=false]

but that does not work either. I will upgrade my distribution too, but it would be nice to have a workaround that works now.

Answer 1

Using my crystal ball you have the viewer problem given in

http://www.latex-community.org/forum/viewtopic.php?f=5&t=7427

https://github.com/josephwright/beamer/issues/142

As far as I understand the transparency and shading issues with PDFs you are better off with a different viewer (I use SumatraPDF) and up-to-date beamer version doesn't show this problem. Thus, it is almost definitely a viewer problem. Using the PS->PDF way is another solution but if you have too many blocks file size will increase a lot and some PS printers will refuse to print your slides.