Bazille Filter FM acting strange

[elnn]

Here's the patch (right-click save) – the G's and G#'s act differently from all other notes – could someone explain why?

If I notch the modulator up an octave, it it changes to Bb's and some other notes.

I tried changing the tuning of the Modulator for the G's and G#'s and it starts working fine, but for intellectual reasons – why doesn't it without this?