You need a QA strategy to match the technology in use. No static type checking means many mistakes will need to be caught in another way. For instance with automated tests, or design-by-contracts. Which might also catch some things that static typing would not cover.
In a non-trivial system with solid engineering, QA concerns quickly go beyond details like which programming language is used. Like how to QA entire systems, sub-system interactions, ensure low time from bug discovered in production to fix deployed, eliminating recurring sources of issues etc.
But if the culture that caused the choice of a dynamic language is "oh its just so much easier and productive to not have to write types all the time!", then you are going to be in for some serious mess and pain in a larger system. That is not a technical problem with dynamic typing/language though :)
That's a very good point: different languages require different QA strategies (do statically typed languages require less unit tests?).
My initial thought when working with Python wasn't from a bugs/QA point of view but merely looking at the productivity of a developer working on a large code-base. Things like accurate auto-complete, code discovery, architectural understanding, knowing what 'kind' of object a function returns and so on become more important once the codebase and the amount of engineers working on it increases.
As another example, consider unsafe/safe like C/C++ versus Java/C#/Rust. Serious systems are built in C (cars, airplanes, medical devices) and it can be done OK - but it requires serious investment in QA, targeted at weaknesses of the language.
In a non-trivial system with solid engineering, QA concerns quickly go beyond details like which programming language is used. Like how to QA entire systems, sub-system interactions, ensure low time from bug discovered in production to fix deployed, eliminating recurring sources of issues etc.
But if the culture that caused the choice of a dynamic language is "oh its just so much easier and productive to not have to write types all the time!", then you are going to be in for some serious mess and pain in a larger system. That is not a technical problem with dynamic typing/language though :)