One SL faulty

Also, since going through the faactory reset with Sonos on the pohone the rattle seems to have gotten more constant!

It’s always frustrating when kit fails, but it does sometimes happen. 
 

That said, I’m surprised by some of your comments in your post.
 

Personally, I don’t know of any other manufacturer that gives discounts off the cost of purchases to replace out-of-warranty items. Yet you feel a 30% discount is “an insult”. Would you prefer it if they offered zero discount? 
 

There’s no reason to expect your other products to fail just because one of them has done so. 
 

Sonos is “an established brand with history and longevity”. They recently celebrated 20 years in business and have a number of innovations they’ve brought to the table over the years. 
 

My main question was if anyone had a diy fix.

It’s clearly a bad build, hopefully it is limited to that item but I have talked to other people that, like me are happy with th sound, but like me feel that Sonos promises a lot else but doesnt always deliver, hardware and software.

If it were anything systemic as a “bad build”, you would see thousands of posts, not one or two anecdotes.  

it is difficult for anyone to suggest a fix without understanding the problem.

You first described it as “crackling” and then as a “rattle”. I appreciate that these can be similar but with audio equipment the difference can be important. I tend to associate crackling with electrical interference or perhaps a failing component. A rattle, to me, is more likely to be something that is loose perhaps in the speaker itself or potentially it could be the stand, if there is one, or a nearby object.

I agree with you that Sonos have significantly messed up in the last year but that does not make their products instantly bad and it certainly does not change the need for a systematic approach to identifying and solving the problem.

Is the crackle/rattle constant or only when the speaker is in use?

Is there a frequency related element to this? (Do certain songs, or sections of songs, seem worse than others)

How does volume impact the issue? (Is it constant or does it increase/decrease with volume changes)

The better you can describe the issue the more chance there is that someone can help.

To answer your que

To answer your question (rather than respond with faux outrage over the tone of your post) you can open up your 1 and inspect for damage. 

See here:

https://www.ifixit.com/Device/Sonos_One

You don’t say which country you’re in, ​@User67738   There is a company in the UK?

People love to infer tone alright. Thanks very much for this, I have given it to someone qualified who will have a go at it.

https://sonosrepair.co.uk/