I agree, safety comes first and no one knows what was done to the structure since 1943, anyway.
One can see a lot of the history, based on age of wood, differences in material. I can say with confidence that the roof structure pictured is 1943 original.
There are two types of safety here: keeping the roofers safe, and keeping the residents safe.
I agree with you on that…
This is for a commercial client, so they cared not at all about the call on the damage, but rather the discussion about what to do next.
The working theory among those present was point loading during re-roofing. There was no sign of similar damage elsewhere, and conveniently if you were to pick a spot to forklift up a load of shingles, this would be the spot.
No records of the prior roofing were provided by the seller. The damaged was pretty clearly “roofed in”, meaning the sag came before the shingles not after.
Thus the preliminary conclusion is : no systemic roof problem. Roof is not strong enough for point loading.