I work with several codebases, (+250Kloc, +150Kloc and 50Kloc), all in Python (plus some bash scripts). The teams working on them are obviously bigger than 3 people. Though they present challenges, I wouldn't consider them "a nightmare", and the number of bugs introduced by the lack of typing are absolutely minimal.

In my opinion, the maintainability of a codebase is not that much a function of the language, but of the architecture and structure of the code.