It could be too much deflection of the joists or subfloor, but I doubt it since modern home must meet L360 deflection standards and that's also the minimum standard for ceramic tiles. But, maybe the subfloor is loose, or just poor workmanship which happens often with builder work.
I think the most likely cause or a combination is that there may not be any expansion space at the perimeter or at certain points in the layout. This is very important in large areas. A tip-off is the sudden stress and the accompanying loud sounds similar to a cupboard full of dishes falling on the floor. Is that kinda what it sounded like? Sometimes it only sounds like one dish breaking, but same reason. The house is shrinking as it dries out and if there's no room, the floor buckles. It's not the house settling I'm pretty sure.
It's called "tenting" and it happens to perhaps thousands of floors every year. I've seen areas tent up about 18" in the center. Others just give all at once and pieces of tiles go flying in the air. I've heard of tiles hitting and even slivers sticking to the ceiling. The sound can be a slight pop or crackle or like an explosion.
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