With bathrooms finished to this standard, the way a repair is carried out matters every bit as much as whether it works.
You may not need to touch the tile
Many valve repairs can be reached through the existing trim plate, or through a small opening in the wall of the room behind — often a closet. Before agreeing to a quote that involves removing stone or custom tile, it is entirely reasonable to ask whether the valve can be reached from behind.
Custom tile cannot be matched
Stone, custom glazes and imported tile are effectively irreplaceable once a line is discontinued. Working around them takes longer and is nearly always the right call.
Multiple outlets on one valve
Larger showers here often have body sprays and more than one head running from a single valve. When one behaves oddly it is usually a diverter or a scaled cartridge rather than a fault with the whole system — worth diagnosing before anyone proposes replacing it.
Leaks reach the room below
A failed pan or drain connection on an upper floor shows up downstairs, and in an empty house it does so unwitnessed. Any sign of staining is worth acting on quickly.