Fade-in/out that wasn't there before?

I have “Sweet Fades” turned off. Up until today (or maybe yesterday), this meant that even when I used shuffle-play on a playlist, there was no discernible fade at either the start or end of a track. All of a sudden, today I’m hearing a brief but noticeable fade-in at the beginning of each track. (It’s obviously more notable when the track itself has a quick start.) I don’t want any fading applied to my music. Is there something I can do to undo this change?

Both my server and my Plexamp client are running on Linux/Ubuntu. I think there was a recent client update (v4.12.2).

Seems like this may be due to the particular “USB soundcard” that I have connected to (some of) my playback devices, not Plex. Beware the Walmart AB13X Headset Adapter if you don’t want this to happen to you!