Only 0's on the input of the custom block

[Bartłomiej Sójka]

Hello,
I'm trying to design custom block that would perform FFT on the incoming signal 
and do some calculations with FFT values later. 
The problem is that while using throttle my signal is reduced to all 0's. If 
it's before the block then the vector with values on the input is reduced to 
all 0 and if it's after the block then the output is reduced to all 0's. It 
seemingly happens at random as the gnuradio schematic sometimes compiles 
without that problem and sometimes, as said, throttle turns all values into 
0's. I know that simple solution would be to not use throttle, but I don't 
think it would solve my problem in a long term. I'm using GNU Radio Companion 
3.10.2.0 (Python 3.10.5).

Best regards
Bartłomiej Sójka