Incorrect symbols/font in Equation (FrameMaker 2015)

Windows 8.1, FrameMaker 2015 13.0.5.547

When using the Equation pod suddenly most characters (Calculus, Symbols, Relations) are displaying as normal characters instead of symbols. No fonts have changed on my desktop to my knowledge.

FrameMaker does not report any missing fonts.

When I export the document(s) to PDF the equations do display correctly.

I have tried purging preferences and font cache and FrameMaker still displays equation characters incorrectly.

Tried uninstalling and reinstalling FrameMaker, no difference.

Equation editing and display is normal in Microsoft Word but I do not know if FrameMaker uses the same font.

Any suggestions would be appreciated.