Nobody calls a contractor about gutters. They call about the water stain on the ceiling, the mulch washed across the driveway, or the crack that showed up in the slab, and the gutters turn out to be the reason.
Start with the sag. A gutter that dips between hangers is holding standing water, and standing water is heavy: about eight pounds per gallon, pulling on fasteners that were probably nailed rather than screwed into the fascia. Once the pitch is gone, the run overflows at the low point in every heavy rain, no matter how clean it is.
Then look at the ground under the seams and the outside corners. Sealant at the miters and end caps is a wear item, not a permanent bond. Drip lines, eroded soil, or a mossy stripe on the wall below a joint mean the seal has let go and the water is now running down the cladding instead of through the downspout.
The third sign is where the water lands. Downspouts that discharge right against the foundation are common on production-built homes and they undo the whole system. In a Carolina downpour a modest roof can deliver hundreds of gallons in an hour into the soil beside your slab. Extensions that carry it four to six feet out are cheap, and they solve more crawlspace moisture problems than any dehumidifier.
The real fix is usually not a repair. If the fascia is soft, the pitch is gone, or the trough is undersized for the roof area it drains, patching buys a season. Seamless gutter formed on site, sized to the roof, hung on hidden hangers with the right pitch, and discharged well away from the house is a one-time job that quietly protects everything under it.