With 2.1.1 and 2.1.2 a new bug is present - I think. I will try to explain:
In Preferences->Audio de-select "Enable Time-Stretching Audio"
Now, when you change the playback speed from 1.00 to (for example) 0.96 the audio takes on a metallic brittle quality that is unacceptable for use.
Previously in 2.0.8 slowing down the audio produced smooth pleasant-sounding playback; there was no metallic quality to the sound. Now (in 2.1.1 & 2.1.2) there is.
This pitch-shift feature is useful for playing back PAL titles at cinema-speed; it is also useful for correcting vintage recordings which may be slightly too slow or fast.
Note 1: I have disabled "use float32" in Audio->Output Modules->Direct X because of the following issue: https://forum.videolan.org/viewtopic.php?f=14&t=114037.
Note 2: when playing back at (for example) 0.96 instead of 1.00, the video may be more jerky than was the case with 2.0.8. I am not sure - this was only a quick impression.