Results/Po​lyspace-Do​c/*.pdf shows only #### instead of text - font problem?

I have upgraded our Polyspace machine from CentOS-5 to CentOS-7 and reinstalled Polyspace 2013a from scratch. Everything works fine, except that after running a verification, the PDF quality report is using '##### ### ## ### ###### ####' (sequences of hashes) where it should show text. Headlines and numbers show properly. The effect is not dependent on the PDF viewer, it looks always like that with xpdf or okular or foxit reader. Moving the PDF to another machine and opening it there shows the same effect.

If I run pdffonts on the PDF, this is what I get:

$ pdffonts Results/Polyspace-Doc/lctsim_Quality.pdf
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
Times-Roman                          Type 1            WinAnsi          no  no  no     286  0
Times-Bold                           Type 1            WinAnsi          no  no  no     287  0
Symbol                               Type 1            Symbol           no  no  yes    288  0

I still have a different PDF created on the old CentOS-5 installation, where it displays fine and pdffonts shows something different:

$ pdffonts sen2b-FM_Quality.pdf
name                                 type              encoding         emb sub uni object ID
------------------------------------ ----------------- ---------------- --- --- --- ---------
EAAAAC+FreeMono                      CID TrueType      Identity-H       yes yes yes    415  0
EAAAAD+FreeSerifBold                 CID TrueType      Identity-H       yes yes yes    421  0
EAAAAB+FreeSerif                     CID TrueType      Identity-H       yes yes yes    427  0

I suspect the problem has something to do with the installed fonts. Can someone suggest how to fix this problem?