removes silence but unwanted speed up or pitch up the output.wav

[pitchsilence]

Summary of the bug:
How to reproduce:

% ./ffmpeg_20190219 -i input.wav -af silenceremove=start_periods=1:stop_periods=-1:start_threshold=-50dB:stop_threshold=-20dB:start_duration=0.0:stop_duration=0.0:start_silence=0.15:stop_silence=0.0 -ac 1 -acodec pcm_s16le -ar 16000 output.wav
ffmpeg version static build 20190219 
built on Ubuntu 18.04/ Linux Mint 19

This removes the silence as expected but add pitch up or speed up (can not say) to the output.wav.
It seemed only to happen, when start_threshold is smaller than stop_threshold (-50dB < -20dB). Maybe it also happens on specific combinations of this two values.
(I didn't tested all possibilities)

[Elon Musk]

This is normal behavior when stop_duration and/or stop_silence is very low: 0.0.

In that case smallest range of influence is single sample, causing such output, even more if window is also 0, which than translates also to single sample.
Set duration options to higher value.