Flickering! – Csound Noobs – Cabbage Audio Forum

I have customized the FFTSpectrum.csd example, removed all unnecessary commands and used guiMode("queue") successfully. I experience a strange flickering problem. The fft spikes on the display flicker! I suggest that the problem is related with csound internal triggers because it happens when signal’s amp and freq come from MIDI, for example

 aSig vco2 p5, p4

On the other hand, FFT spikes are steady when I set them up numerically in the orc section, for example

 aSig vco2 .7, 220

Here is a copy of all significant commands

<Cabbage>
form caption("FFT Spectrum"), size(610,570), colour( 50, 50, 50), pluginId("spec"), guiMode("queue")
gentable outlineThickness(1), bounds( 0,  0, 610,300), tableNumber(1), tablebackgroundColour("white"), tableGridColour(100,100,100,50), tableColour(0,0,200,200), channel("ampFFT"), ampRange(0,1,-1), outlineThickness(0), sampleRange(0, 512), zoom(-1) 
</Cabbage>
<CsoundSynthesizer>
<CsOptions>
-n -d -+rtmidi=NULL -M0 --midi-key-cps=4 --midi-velocity-amp=5
</CsOptions>
<CsInstruments>
ksmps = 32
nchnls = 2
0dbfs = 1
;...
instr 1
;...
; signal generation
 aSig vco2 p5, p4
;...
 if  metro(16)==1 then
  kflag  pvsftw fSig2, iampFFT
 endif
 if kflag==1 then
  cabbageSet	1, "ampFFT", "tableNumber", 1	; update table display
 endif
;...
endin

</CsInstruments>
<CsScore>
;causes Csound to run for about 7000 years...
f0 z
i1 0 [3600*24*7]
e
</CsScore>
</CsoundSynthesizer>