How to force retry when an apt install has failed ? APT::Acquire::Retries does not seem to work

Question

I am working with a corporate repository mirroring canonical repository. I suspect that this corporate repository is not reliable, because I have sporadic failures such as:

Failed to fetch ...  502  Bad Gateway [IP: ...]
Failed to fetch ...  404  Not Found [IP: ...]

It does not seem to depend on the package to be installed. Taking that into account, I tried to use APT::Acquire::Retries:

RUN echo 'APT::Acquire::Retries "3";' > /etc/apt/apt.conf.d/80-retries

(and yes, I am building a docker image)

Here's how I am installing the packages:

...
    && apt install --no-install-recommends -y \
        curl \
        apt-utils \
        iputils-ping \
        nano \
        gridsite-clients\ 
...

I have the feeling that the APT::Acquire::Retries is not taken into account (ie by using higher values such as 30 ...).

The base image used is an ubuntu:20.04, with a version of apt equal to apt 2.0.8 (amd64).

Any clues ?

[Edited] By activating the following tweaks on apt.conf, I managed to get rid of 502 errors:

RUN echo '\
Acquire::Retries "100";\
Acquire::https::Timeout "240";\
Acquire::http::Timeout "240";\
APT::Get::Assume-Yes "true";\
APT::Install-Recommends "false";\
APT::Install-Suggests "false";\
Debug::Acquire::https "true";\
' > /etc/apt/apt.conf.d/99custom

In which case (read http status cod errors) Acquire::Retries works ?