pdf2htmlEX error during conversion - CMap is not valid and got dropped for font - pdf2htmlex

Question

I'm using this version https://github.com/pdf2htmlEX/pdf2htmlEX/releases/tag/v0.18.8.rc1
this debian version pdf2htmlEX-0.18.8.rc1-master-20200630-Ubuntu-focal-x86_64.deb
When I run the conversion I get a bunch of these errors:
Working: 97/100ToUnicode CMap is not valid and got dropped for font: b7
which result in empty files, without any text.
I'm running via docker, this is my dockerfile:
FROM ubuntu:20.04
RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
ENV DEBIAN_FRONTEND=noninteractive
RUN dpkg --configure -a
RUN apt-get clean
RUN apt-get update
RUN apt-get install -f -y python3
RUN apt-get install dialog apt-utils -y
RUN apt-get install -f -y python3-pip
RUN apt-get install -f -y python3-setuptools
RUN apt-get install -f -y wget
RUN apt-get install -f -y poppler-utils
RUN apt-get install -f -y poppler-data
RUN apt-get install -f -y jq
RUN apt-get install -f -y zip unzip
RUN apt-get install -f -y pdftk
RUN apt-get install -f -y ffmpeg
RUN apt-get install -f -y libfontforge-dev
RUN DEBIAN_FRONTEND=noninteractive; apt-get install -f -y pdftk-java
RUN apt install -f -y ghostscript
RUN pip3 install --upgrade pip \
&& apt-get clean
RUN pip3 --no-cache-dir install --upgrade awscli
WORKDIR /tmp
COPY lib/pdf2htmlEX-0.18.8.rc1-master-20200630-Ubuntu-focal-x86_64.deb /tmp
RUN apt install -y ./pdf2htmlEX-0.18.8.rc1-master-20200630-Ubuntu-focal-x86_64.deb
RUN wget https://www.imagemagick.org/download/ImageMagick.tar.gz && \
tar -xf ImageMagick.tar.gz && \
cd ImageMagick* && \
./configure && \
make && \
make install && \
ldconfig /usr/local/lib
Please advise how can I resolve this?