Think of it as overly aggressive error correction at the language level.
It has a context of some Base64 code. Given that is almost always seen associated with computer code, is "address" or "actress" more likely.
It "knows" the algorithm for decoding base64, and can follow those steps. But it can't overcome it's built-in biases for optimizing the most likely output given the context.
(This problem is solvable, but I think that thinking about it like this helps understand why it behaves like it does)
This is all irrelevant. A language model should not run code itself, instead it should have a code execution environment, where it can read the error messages and iterate. It's terribly inefficient and error prone to run code directly.
The point is to develop good intuitions for how large language models behave. If someone can develop a differentiable script runner that would be great! But the intuition about how the language model is behaving is useful for more than this specific problem.
It has a context of some Base64 code. Given that is almost always seen associated with computer code, is "address" or "actress" more likely.
It "knows" the algorithm for decoding base64, and can follow those steps. But it can't overcome it's built-in biases for optimizing the most likely output given the context.
(This problem is solvable, but I think that thinking about it like this helps understand why it behaves like it does)