Permission error when using --cmd or --entrypoint instead of --exec. Ideas highly appreciated

Expected Behavior

I'm running a daemon in a docker container, so I need to run it for a longer time and then tell docker-slim when analysis is done (e.g. via enter or signal).
Running
docker-slim build --target IMAGE --tag IMAGE:0.0.5-slim --http-probe=false --exec='my daemon'
Executes the command correctly and it does not crash with the permission issue, but my daemon never exits, so it is not the right usage here.
Instead of using --exec I need to use --cmd (or --entrypoint), interact with the container and stop analysis manually.

Actual Behavior

However, neither --cmd='my daemon' nor --entrypoint='my daemon' work. In both cases, the execution shows a permission error inside the docker container, while apparently the same command is being executed like with --exec

My thought the user may not be set properly, but at least stdout shows me that docker-slim properly identifies the USER directive present in the Docker image

Steps to Reproduce the Problem

This is an internal tool so I can't share too many details here unfortunately. I'm happy to share more if someone can point me to output that would be of help here.

Specifications

cmd=version info=app version='darwin|Transformer|1.36.1|d8f2be23d44bf9f96c5f1f7e970c739106d17996|2021-06-21_03:24:08AM' container=false dsimage=false
cmd=version info=app outdated=false current=1.36.1 verdict='you have the latest version'
cmd=version info=app location='/Users/USER/gdrive/tools/docker-slim'
cmd=version info=host osname='Big Sur (11.5)'
cmd=version info=host osbuild=20F71
cmd=version info=host version=' Sat May  8 05:10:33 PDT 2021; root:xnu-7195.121.3~9/RELEASE_X86_64'
cmd=version info=host release=20.5.0
cmd=version info=host sysname=darwin
cmd=version info=docker name=docker-desktop
cmd=version info=docker kernel_version=5.10.25-linuxkit
cmd=version info=docker operating_system=Docker Desktop
cmd=version info=docker ostype=linux
cmd=version info=docker server_version=20.10.6
cmd=version info=docker architecture=x86_64
cmd=version info=dclient api_version=1.41
cmd=version info=dclient min_api_version=1.12
cmd=version info=dclient build_time=2021-04-09T22:44:56.000000000+00:00
cmd=version info=dclient git_commit=8728dd2

Start with the reported docker-slim build invocation and compare execution with --exec, --cmd, and --entrypoint using a daemon container. Reproduce the permission error, capture the container output, and verify that the daemon can be stopped interactively without the permission failure.