If you just make any signal source and a QT GUI
Sink, you'll see that the frequency scale is wrong: a 32ksps signal will
show a frequency range from -8kHz to +8kHz (instead of -16...16kHz).
Also, if you keep the default FFT size of 1024, the chooser widget shows 256, but in reality the FFT size is correct at 1024. If you select 1024, nothing changes. Going back to 256, the spectrum becomes coarser.
BTW, I can zoom in/out in the FFT view using the scroll wheel, but I can't move up/down. By default I just see the frequency peak of the synthesized sine wave, not the noise floor.
Greetings,