Program stalls on "DEBUG Starting new HTTPS connection (1): login.microsoftonline.com:443" only when executed via cron - docker-compose

Question

I'm using the python-O365 library in order to access my O365 mailbox. The project requires me to execute the program in a docker container. If I start the program manually (as root), everything works fine, but if I try to start it via cron, it stalls on DEBUG Starting new HTTPS connection (1): login.microsoftonline.com:443, which I found out after activating logging.
The minimal code example that reproduces the error (with log):
import O365
from utils.credentials import get_credentials
import logging # We want to get additional information
logging.basicConfig(
filename='./easy_log_file.log',
filemode='a',
format='%(levelname)s %(message)s', # %(asctime)s %(pathname)s %(lineno)d
level=logging.DEBUG
)
filename = "o365_token.txt"
token_backend = O365.FileSystemTokenBackend(token_path = filename)
account = O365.Account(get_credentials(), token_backend=token_backend)
inbox = account.mailbox().inbox_folder()
messages = inbox.get_messages()
for message in messages:
logging.info(message)
logging.info("finished")
To start it via cron, I used the following command:
echo "15 21 * * * bash /workspace/daemon_start.sh >> /workspace/cronlogs/logs_daemon_mail.log" | crontab. If I start the program manually, the log continues like this:
DEBUG Starting new HTTPS connection (1): graph.microsoft.com:443
DEBUG https://graph.microsoft.com:443 "GET /v1.0/me/mailFolders/Inbox/messages?%24top=100&%24filter=isRead+eq+false HTTP/1.1" 200 None
DEBUG Received response (200) from URL https://graph.microsoft.com/v1.0/me/mailFolders/Inbox/messages?%24top=100&%24filter=isRead+eq+false
If the program is started via cron, sometimes the log continues like this:
DEBUG Incremented Retry for (url='/common/oauth2/v2.0/token'): Retry(total=2, connect=3, read=3, redirect=None, status=None)
WARNING Retrying (Retry(total=2, connect=3, read=3, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1131)'))': /common/oauth2/v2.0/token
In order to resolve the issue, I added my proxy by using account = Account(credentials, token_backend=token_backend, proxy_server="proxy.my_proxy.com"). It's strange, that I would have to add it, for the container is already configured to use this proxy. When I tried it with this setting, I encountered the same issue, only that the log when started with cron was continued always and much faster.
Since I think, that cron simply starts the program and does not meddle with the connections, it doesn't make sense to me, that I get different outcomes by starting it manually or with cron.