Gutted for you
If it were me, I'd gather every dictionary definition of wear & tear I could find, most of which say (often somewhat more lengthily admittedly) "Gradual physical deterioration of an asset through age, use and / or weathering".
I would then argue that this frame crack is clearly not a gradual deterioration, but rather a failure - and most likely a sudden one at that - and ask them to reconsider their decision, with all of the information that you have provided very much in mind.
Good luck
If it were me, I'd gather every dictionary definition of wear & tear I could find, most of which say (often somewhat more lengthily admittedly) "Gradual physical deterioration of an asset through age, use and / or weathering".
I would then argue that this frame crack is clearly not a gradual deterioration, but rather a failure - and most likely a sudden one at that - and ask them to reconsider their decision, with all of the information that you have provided very much in mind.
Good luck