I don't think that's the problem, at least not directly for us. The immediate interface between the languages is handled by a binding layer (e.g. pybind11 or nanobind), but that rarely lets you fully express object relationships (something that would be more possible without the binding layer) so it is very easy to either not capture ownership (and thus the C++ object is destroyed out from underneath you) or express a cycle that cpython can't understand (and thus the C++ objects are never destroyed and can leak a significant amount of memory). Explicit manual control would avoid that, but at a level of work that would be prohibitive of having extensive bindings in the first place.