MP3 loudness varies between tracks on same album

Server Version#: 1.21.1.3842
Player Version#: 4.47.3

Hey all, I’m fairly new to Plex and am loving the service so far.
I started out digitizing our movie and show content, but have now started adding my old MP3 music library and have come across a volume issue.
I’ve tried various searches in the forums and on google but can’t find anything about the issue I’m having.

The music library I’m slowing adding to my PMS (Windows 10 desktop) was originally ripped from CD’s via iTunes (going back many years), then later uploaded from iTunes to Google’s Play Music, then recently downloaded as a complete archive from Play Music (created 28 separate 2GB zipped folders), so all these tracks/files have “been around”.

My issue is when recently listening to Bad Religion’s “Suffer” album, streaming to my iPad via wifi on my local (home) network, there was a sharp decline in playback volume from the first two tracks to the third one, causing me to turn up the volume on my stereo receiver (connected via Bluetooth), but when track 6 came on it was really loud again, forcing me to turn down the receiver volume.

After searching for an answer I dug deeper into the files themselves (from within my PMS interface - “get info” on each track) and found that for some reason while the “album gain” was consistent across all tracks at -12.38 the “loudness” values varied widely as follows:
T1 -6.23
T2 -6.18
T3 -15.37 (the volume dropped and I turned up my stereo)
T4 -15.66
T5 -16.03
T6 -6.17 (the volume came back up and I had to turn the stereo down)

This volume variation continued through the rest of the album (as does the loudness value on the files), with my turning the stereo up and down as needed.

After reading some about normalization and loudness leveling, I thought this loudness variation might have something to do with the “analysis” that Plex apparently does, but clicking “analyze” again for both the album and the individual tracks did nothing.

Any idea what is causing this? Is there a “simple” automated fix?
I might even be willing to simply edit these values manually as needed if the issue isn’t too widespread (haven’t noticed it with other albums so far), but I’m not even sure how to do that.

I appreciate any feedback!

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