Hi Andy, and thanks for continuing to keep this site going - very handy
Let me see if I can find the research I did on this on my PC.... [10 minutes later] sorry can't find the actual review which mentioned this.
However I do remember the details - the customer had the same issue as me (Miele FF conked at 2.5 years) and a decent Miele repair guy had said that they estimated about 1-2% of the FFs came out of the (Liebeherr?) factory with this as a potential inherent defect (something to do with the gas and tubing) and that the main way to recognise a faulty unit was the type of noise coming from the rear. Personally I always leave 24 hours before switching on any fridge unit after moving, so not due to that!
Apologies, I might have been too vague in saying that a 'cracking' noise was a definite indicator - as you say, even the replacement model I was given (and which has worked fine for 7.5 years) makes a cracking sound now and then. Looking back, the noise from the first, faulty model was much louder and sort-of-different.
I think the review I noticed was actually left on the Which? website - interestingly Which? took the unilateral decision to stop allowing people to comment on Product Review pages, probably because so many (coherent) reviews were posted contradicting their glowing reviews (including Which? members who pay almost a £10 a month for their sub). Which? had reviewed lots of Miele FFs and given them Best Buy status a few years back - then all of a sudden they seemed to stop reviewing the brand range, which seemed odd. At the moment there are only 1-2 listed.
As much as, like you, I love my Miele for its washing performance and solid feel, if you haven't gone over and looked at the Miele Great Britain pages on Trustpilot, worth doing - in between the usual unrealistic ranters there is quite a fascinating thread of customer experiences!
(For balance, have to say my fairly basic Miele dishwasher has worked faultlessly for almost 10 years, as has my 15 year old Miele vacuum with powered head).
Wonder if Miele allow customer visits to their washing machine factories these days? Always enjoyable to see how things are made.