True gapless playback not working

I re-split the MP3s from the source MP3 and CUE using this mp3splt command:

mp3splt -f -b -T 2 -o '@n  @p - @t' -d output -c input.cue input.mp3

I didn’t use the -f and -b options last time I split this file (I don’t think -b existed at the time):

 -f   Frame mode (mp3 only): process all frames. For higher precision and VBR.
 -b   [Experimental] Bit reservoir handling for gapless playback (mp3 only).

I think this fixed it. I did the “Plex Dance” and cleared my local cache (took a while to find but eventually I used Process Monitor to watch where Plexamp wrote its files, and found the cache at C:\Users\Daniel\AppData\Local\Temp\Plexamp\Caches\Media). At first I thought it didn’t fix it, but it was because I forgot to clear the Plexamp cache so it was still playing the ‘old’ version from the cache.