Update/solution- So thanks to Daves post above it got me thinking about this scratching/buffering appearing for me around the time I cancelled premium connectivity- in the UK teslas have ‘TuneIn’ radio, I’m not sure if other countries have the same app?… but anyway, tunein has all the dab/fm radio stations that I listen to, plus lots of ones you can’t get on DAB/FM, but it uses data rather than a traditional aerial, and is only available with premium subscription.
I’ve re-subscribed to premium and Tune-In doesn’t have any of the scratching/buffering that DAB/FM has, even adjusting volume is completely problem free. So for me the £9.99 a month to get crystal clear audio again is my solution, not perfect as it costs, but at least it works!
Thinking back, I always used TuneIn instead of DAB / FM before I cancelled premium a few months ago, so the dab scratching could have always been there, but as I never used it, I’d have never heard it.
I hope this helps someone else in the same situation