Wild guess: It realised its mistake partway through, and followed through it anyway as sensibly as could be done, balancing between giving a wrong calculation (“+ 12 = 41“), ignoring the central focus of the question (” + 12 = 42”), and breaking from the “list of even integers” that it was supposed to be going through. I suspect it would not make this error when using chain-of-thought.
Wild guess: It realised its mistake partway through, and followed through it anyway as sensibly as could be done, balancing between giving a wrong calculation (“+ 12 = 41“), ignoring the central focus of the question (” + 12 = 42”), and breaking from the “list of even integers” that it was supposed to be going through. I suspect it would not make this error when using chain-of-thought.