Hi.
It's been ages and nobody has noticed this, so I'm reporting.
I'm using Xiaomi Mi A3 but this has also occurred on another device.
I'm referring to mp3 but this also happens with wav (not tested with other formats)
When the playback starts (i.e. I choose the file or use the seek function, doesn't occur for the replay function) the playback pitch does a bit down and then after a while a bit up (higher than nominal) to compensate the previous loss of playback time probably (I'm thinking the playback speed is affected, but I can't tell since my tempo hearing ability is not as good as musical hearing).
This hasn't happened to me since the tapes and vlc is the only one out of some ten players I've been trying out.