Bought the WH-1000XM3 headphones in July this year, very happy with them. Using them today as normal and adjusted the straps as you do - then the left strap  broke off under completely normal use. This has me worried after reading a few other posts for the same issue on this forum as Sony will probably want to charge me to fix this because of the low quality materials they have used in £300 headphones? I bought them from Amazon and notice a few reviews on there with the same issue reported.  The left strap broke in this case and no longer adjusts. Amazon directed me to Sony for warranty purposes but have the feeling I will need to push Amazon for a replacement instead. Wanted to let people know about this and to think again before buying them.