[tex4ht] How to best find cause of Illegal storage address?

[Nasser M. Abbasi]

I changed the document style from article to
\documentclass[12pt,chapterprefix=false]{scrbook}

And since this happened, now I get

---------------------------------------------
Output written on index.dvi (1851 pages, 10984724 bytes).
Transcript written on index.log.
Make4ht: tex4ht  -cunihtf -utf8 "index.dvi"
----------------------------
tex4ht.c (2018-07-03-10:36 kpathsea)
tex4ht -cunihtf
   -utf8
   index.dvi
(/usr/local/texlive/2019/texmf-dist/tex4ht/base/unix/tex4ht.env)
(/usr/local/texlive/2019/texmf-dist/tex4ht/ht-fonts/unicode/charset/unicode.4hf)
(/usr/local/texlive/2019/texmf-dist/fonts/tfm/public/lm/rm-lmtt10.tfm)
(/usr/local/texlive/2019/texmf-dist/tex4ht/ht-fonts/alias/lm/rm-lmt.htf)
Searching `lm-ec.htf' for `rm-lmtt10.htf'
(/usr/local/texlive/2019/texmf-dist/tex4ht/ht-fonts/unicode/lm/lm-ec.htf)
--- error --- Illegal storage address
Make4ht: Fatal error. Command tex4ht returned exit code 256
--------------------------------------------

Since I can't make a MWE (the file is about 1,500 PDF pages)
what would me a good way to debug this to find why it happens?

Is there a way to turn-on additional messages?

It will take me forever by trial and error to know why it happens
otherwise.

I could make the whole file and all the images available
and the command I used, which is

make4ht -ulm default -e /home/me/new.mk4
     -c /home/me/nma_mathjax.cfg index.tex
     'htm,3,mathjax,notoc*,p-width,charset=utf-8' ' -cunihtf -utf8'

and put everything in a zip file if someone wants to try. Now,
I do not know where else to look. It might be a font issue,
it always fails right after  "....lm-ec.htf" line

TL 2019 on Linux windows subsystem.

Thanks for any suggestions
--Nasser