Between late October and early April, the ground along the Wasatch Front freezes at night and thaws in the afternoon over and over. Every one of those cycles is a small pumping action: water in the soil expands about nine percent as it freezes, lifts whatever is above it, then releases when it thaws. Do that a hundred times a winter and anything sitting on unstable ground moves.
That is why a paver patio built on two inches of loosely dumped road base looks fine in September and looks like a wave by May. The pavers themselves are almost never the problem. The base is.
A base that holds up here starts with excavation deep enough to get past the topsoil and any soft fill. Under a patio we want a compacted aggregate base four to six inches thick, and under a driveway considerably more. The important word is compacted, and the important detail is that it happens in lifts: three inches of base, compact, another three inches, compact again. A plate compactor cannot densify twelve inches of loose rock in one pass no matter how many times you walk it.
On top of the base goes a thin, screeded bedding layer of coarse sand or chip, not a thick cushion. Bedding is there to seat the paver, not to make up for a base that is out of level. Anything more than about an inch of bedding just gives the pavers somewhere to sink into.
Then the edges. An unrestrained paver field spreads outward under traffic, which opens the joints, which lets in water and sand, which lets the field spread further. Concrete or spiked edge restraint on every open edge is what stops that cycle before it starts. Polymeric sand in the joints does the rest, locking the pavers together and keeping weeds and ants out of the seams.
None of this is exotic, but all of it takes time and it is the part that disappears the moment the first paver goes down. When you compare bids for a patio, the number to ask about is not the paver style. It is the base depth, the number of compaction lifts, and how the edges will be restrained.