So after fewer than 62 days use my WF-1000XM3s have developed an ear bursting fault.  Tried to use the right earbud to take a phone call, and on inserting it got a really loud high pitched whine in my ear.  Left bud was fine.

Now after a day or so more, and some experimentation it happens after 5 seconds with the right bud.  If I tap the NC mic it goes away, but returns about 10 seconds later.  Doesn't happen with NC set to any ambient mode.

Also if I take the silicone eartip off it happens instantly, on either bud.  John Lewis insisting they're sent back for repair as theyre >30 days old, which doesn't sound right. Waiting to find out if it's a Sony repair or some 3rd party repairer they use.

Not managed to find any reports of similar issues so assume I'm just unlucky.  Never been used outdoors, never been dropped or subjected to moisture so I've no idea why it's started to happen.