Sometimes when I play songs through VLC on android the sound slowly wobbles and stabilizes after a while. This seems to happen usually on the first song played but I'm not too sure about that. Sometimes I force close VLC and clear the cache and launch it again but it does not seem to produce it again. I've had this happening with two different Android phones by different manifacturers so I doubt it's hardware issue.
This has occured with formats like WAV and FLAC at least. I didn't do crazy tests on other formats.
Here's an image with the spectrum visualizing the wobble. It starts at 0:02 and ends at 0:42. The clip itself here is 0:52 but the original clip that I recorded from the device was around 3:00. I'm mentioning that just in case as I do not know and haven't tested if the lenght of the clip has any effect on this behaviour.
The pitch offset from the origin peaks at -25 and 23 cents.