Issues with gapless playback iOS 17

For years I've been having problems with gapless playback on iPhone (iPhone 12 Pro, iOS 17.0.3), specifically with albums ripped from CD. It appears to be happening mostly when syncing libraries with iTunes Match and now with Apple Music, even when the albums have been downloaded to the device. All albums were ripped using iTunes or more recently Music on a MacBook Pro using the default setting (256kbps .m4a). I have tried re-ripping them with no success.

Advice from an Apple technical advisor was to disable library sync on both iPhone and MacBook, connect iPhone to the computer and transfer the albums to it via the lightning cable. This worked for a time but when library sync was switched back on the problem returned, and on one occasion it bizarrely removed the download. Additionally, some albums are fine but others not, and it's totally random. I can delete all music then re-transfer the music to my iPhone and the problem will occur on different albums. As far as I can tell, none of them play back gapless on Apple TV or on iPad.

I don't have the time of patience to experiment with re-ripping albums in different formats, does anyone have any other ideas?

It's a pretty poor show when you consider that my crappy old MP3 player could play these albums ripped from CD with gapless playback almost 20 years ago.

There's another post on this issue here