Firefox v71 and PDF Readers

I am using a Windows 7 Pro  32 bit PC with Sandboxie 5.30 installed.

Before the recent Firefox update I had Firefox set up to read PDF documents.

With the new update to FF v71 when I run FF Sandboxed and I click on a PDF file a window pops up asking me to select the program that I want to open the PDF file in.

The radio button to make the program the deafault is always ticked but every time I go to view the file the same window pops up.

This does not happen when I run Firefox Un-sandboxed.

Is there anything that I can do to remedy this situation?

Has anbody else experienced this?


PS. I also have a Laptop running Windows 7 Home 32 bit, the same thing happens there.