Halo, ran into a crash on macOS on v0.9.1, ~15 min in. segfault in the main loop, GDScript calling .size() on what looks like a null Array during a _process tick.
stack bottoms out at Array::size() → inner GDScriptFunction::call → Object::_notification_forward (process notification) → SceneTree::_process_group. so it's a per-frame script doing something.size() without a null check.
probably worth grepping your _process funcs for .size() calls on arrays that get cleared/reassigned. cheap fix is if arr: arr.size() or default to [] instead of null.