Flexbond and even Mega Flex (a great thinset product) WILL NOT stop cracking tiles under these conditions. Those thinsets are used for lateral flexibility between a substrate and a tile strata and are used to help absorb expansions and contractions.
I suspect the major movement here is not from expansion and contraction of materials but instead from instability of the overall structure and style of construction.
Yes, maybe rigid tile installations should be avoided in the future. Not all structures are suitable for tile installations.
