I have a XM3 pairs for a couple of years and both side of the headband have fractured multiple places. Both of the sides have a small “clip” on the inside that have broken of. This have resulted in that one of the outside covers have split across. They are currently being kept together with strips, but I have to be careful that the strips does not slid off.
The issue apparently stems from me opening/spreading the headphones a bit to much when putting them on. Nothing else. They have otherwise always been in their case.
The official repair cost almost the same as a new pair, and second-hand replacement, as seen herecost way too much compared to the quality.