The main problem with duck-typing like python has is the lack of consistency between different objects that code has to work on. Different callers may pass objects with different sets of methods into a function and expect it to work. You run into the case where the object that was passed in is one with subtly-mismatched behavior from what your method expects, but you don't know who created it - it was probably stored as a member variable by something 10 callstack levels and 5 classes distant from what you're currently working on.

Static typing prevents that by telling you early where the mismatch is happening - some method calls into another with a variable of the wrong type, and that's where the bug is. It also allows tooling to look up the types of variables and quickly get information about their properties.