When I am playing music in the web player on my Windows PC in Firefox 86 (64 bit) from my server (FreeBSD 12.1, Subsonic 6.1.6, Tomcat 9.0.37, java 1.8.0_265), the audio drops out for about 10 seconds at a time. The player looks normal, with the song progress ticking up; then the music comes back on its own. This can happen between 0 and 5 times for a song, and generally doesn't happen more than once a minute. This appears only to happen when I am listening to FLAC music. My transcode command is "ffmpeg -i %s -map 0:0 -b:a %bk -v 0 -f mp3 -" which I believe is the default. Ffmpeg is from the pkg repository. There are no entries in the Subsonic log for anything besides registering songs on Last.fm.
If I listen to a song again, the audio drops in the same place(s). I have ideas about what might be happening, but I don't know what to try to fix it.