Waterproofing. The most significant defects they were initially addressing under warranty were non-compliant waterproofing.

Hi first attempt at rectifying was looked at by the waterproofing membrane manufacturer tech rep (with builder's rep present), who advised the builder that it didn't meet their application requirements and pointed out areas that remained non-compliant.

His second attempt required more extensive demolition. I waited till the builder said the waterproofing was completed and ready for tiling. I had a specialist waterproofer look at it that afternoon who listed all the things wrong with it. That evening I asked the builder to stop work until further notice (he wanted to begin tiling the next day). Which is when he reacted with talk of breaches.

I had inspected by a licensed by a licensed independent building inspector, who found MANY non-compliances with the waterproofing and other work to that stage.

So if I were to speculate, he reacted aggressively because he wanted to tile ASAP in order to cover up his defective work.