When a new floor starts gapping, clicking, or cracking within a year, the cause is almost always the same: the slab underneath wasn't flat. Most flooring manufacturers require the subfloor to be within about 3/16 of an inch over ten feet, and plenty of South Florida slabs are nowhere close.
We check every floor with a long straightedge and a level after demolition, and we mark every high and low spot. High spots and old thinset ridges get ground down. Low spots get filled.
For deep, localized dips, we use mortar or patching compound troweled flat. When a whole room is out of level, we prime the slab and pour a self-leveling compound that flows out into a smooth, flat surface and cures hard enough to install on.
For tile, we also use a leveling clip system during installation. The clips hold neighboring tiles at the same height while the mortar sets, which eliminates lippage, those uneven edges you can feel with your foot.
Leveling adds time and cost, which is why some installers skip it. We build it into the estimate from the start, because a floor that's installed on a flat base is the one that still looks right years later.