I discovered today that the normalize and dot product nodes in the material editor, in certain combinations, give incorrect outputs.
In the screenshot below, I show dot products of unit vectors in different combinations, with and without being passed through the normalize node. In most cases the result is 1.0, as expected, but in one of the examples, it is not.
In the screenshot below, I calculate the length of a unit vector before and after normalization, both manually and using the dot product node. After the normalize node, the dot product node gives a different result than manual calculation.