It seems like the bot stops working sometimes while watching patchsets; most likely due to a timeout issue with the ssh paramiko client that the bot uses. As a workaround whenever this happens, I learn about it via a text message and restart the bot. Earlier, it used to be once a month issue, but it has been a bit frequent recently. Background conversation: https://github.com/srish/gerrit-newcomer-bot/issues/10.
This needs help from an expert who understands the underline structure of paramiko (http://www.paramiko.org/) and could help fix this problem.
https://github.com/wikimedia/labs-tools-gerrit-newcomer-bot (mirrored version)