Bibliography issues

[Rich Shepard]

I'm using lyx-2.3.6.1 and the (older) document class is KOMA-Script Book.

A while ago I changed the bibliography generator from bibtex to biblatex,
but that's not an option for this document; only Default, biber, bibtex, and
bibtex8 are available from the Settings -> Bibliography dialog box. See
attached bibliography dialog box image.

When I try to compile the document (pdflatex) I find old-font-type errors
(see attached build error image.) Those should have been corected long ago.

Recent documents using the report classe haven't had these issues.

I need a pointer to find where I start looking for the reasons of these
issues.

TIA,

Rich
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