Your attic: Termites like attics here in Phoenix because they’re a source of accessible, exposed wood in a relatively undisturbed place. Look for mud tubes branching out between beams: this is how some termites travel from beam to beam.
I'm not familiar with termite damage and was surprised to find this (Link). The torn top plate resting on the backing looks odd though it may be a combination of insulation, wood, and sunlight.
Arizona doesn't have a blowing sand issue. They have lots of vegetation in their desert. Monsoons are another story. Arizona is one of the regions that gets all of its annual rain within a few hours.
They can weigh over a ton. quite often just hung on two suspension points.
Personally I would design just for them at the starting point then the rest of the roof round them.
If they were added in post design and build they are an accident waiting to happen as they may get a tick for 3 lanterns but then get progressively added too as pastors change and the history of them is lost.
I am wondering what the trigger was for the buckling. Something added recently or an environment change
As i roll this over in my mind, the structural defect could be as basic as not having solid blocking between the trusses where they sit on the west wall ... and two of them rolled over.
I am venturing an educated guess based on photos 'cause we have to start somewhere. It helps to be informed rather than just waiting on expert reports, which could be less than adequate.
I'm still not totally understanding the framing here. There's a change in slope in the ceiling, but not the roof. So these aren't fully parallel chord trusses. (ETA I'm not sure this line is correct - think eyes playing tricks)
And the broken pieces that are now poking up at the outside bearing wall look more like joists than the remnants of a top chord extension. That hardly seems like enough depth to make truss work for that span.
Could there be another beam at that slope change? Doesn't seem likely.
