Trashed synth Beep() sounds

[hexaae]

Hi,
if I set "Sound" (WB3.9) to make WB use a synth beep on error, I can hear a trashed sound from WINUAE 2.3.x in normal WB usage when an error occurs (e.g. attached Beep exe. Or when you try filename-completion with KingCON for a wrong command). This happens only for the first 2-3 times, like a kind of trashed data buffer to be flushed first, and then starts to emit the correct synth beep sound, untill next reboot.... Hope someone understands what I mean
Notice that I can perfectly hear synth chip tunes with Delitracker 2...

Here are my WUAE config settings:

win32.soundcard=0
win32.soundcardname=WASAPI:Default Audio Device
win32.soundcard_exclusive=false

sound_output=exact
sound_channels=stereo
sound_stereo_separation=8
sound_stereo_mixing_delay=0
sound_max_buff=4096
sound_frequency=48000
sound_latency=100
sound_interpol=none
sound_filter=emulated
sound_filter_type=enhanced
sound_volume=20
sound_auto=false
sound_stereo_swap_paula=true
sound_stereo_swap_ahi=true