PDF export unexpectedly results in widespread character encoding glitches in the PDF document.

This is a new issue, never encountered before.
Character glitches (odd characters) display at the end of a line (line break ?) mostly after bold text
Document is in English, no other languages.
Gltiches (weird characters) not happening on special characters.
Document uses standard fonts
Gltiches appear in Acrobat and Chrome / Firefox PDF viewers.