The patch was probably in the wrong place
Water comes through the covering, lands on the deck or a rafter, and runs. Sometimes a few inches, sometimes the width of a room. It soaks through the ceiling at the first low point it finds, and that is where you see it.
So the stain is downhill of the entry point, and often to one side of it. Anyone who treats the stain as the location is sealing a part of the roof that was never leaking. The ceiling dries because the attic dried, not because the water was stopped.
Then it rains hard enough again and the same path fills. Nothing has changed on the roof, so nothing has changed inside the house. The repair was real work on real material. It was just not on the hole.
The patch held. The water was never coming through there.
Sealing the surface over a joint that moves
Flashing, valleys and penetrations are the three places a roof leaks most, and all three are joints rather than surfaces. A wall tie-in, a chimney, a skylight, a plumbing vent boot, the line where two slopes meet. They carry concentrated water and they move with every heat cycle.
Sealant spread across the top of one of those closes the gap for a while. Then the joint expands, contracts, and the compound hardens and cracks — faster here than almost anywhere, because of the heat and the UV. A reopened sealant line looks exactly like a new leak and is the old one.
The difference between the two repairs is whether anything came apart. Correcting a flashing detail means lifting the covering, finding out how the metal is lapped and where the water is getting behind it, and putting the laps back in the order that sheds water. That is a repair that works because the joint is right, not because something sticky is holding across it.
Caulk has its place in roofing. Holding a moving joint watertight on its own is not that place.
One failure point, or underlayment that is finished
There are two situations that produce the same drip, and they do not have the same answer.
The first is a single failure point. A split vent boot, one flashing joint, a cracked tile over a valley, a nail that has backed out. The rest of the roof is shedding water. Fix the one thing and the roof goes back to working, and it stays working.
The second is widespread underlayment failure. The layer under the covering is what actually keeps water out of the house once anything gets past the surface, and when it has gone brittle across the roof, water finds a new way through every time it rains hard. This is the case people describe as a leak that moves. It is not moving. There are several, and you are only seeing the one that reaches a ceiling.
Tile is where this is most often misread, because the tile itself can be sound while the underlayment beneath it is done. A roof like that can look excellent from the street and leak in a different room each season. Patching it one spot at a time is a treadmill, and we will say so rather than sell you the next patch.
How a roofer works backwards to the source
Start inside, on a dry day, with a flashlight. The attic holds the history. Dark staining, salt lines, rust on nail points and truss plates — that is the path the water has been taking, and it is still readable long after everything has dried.
Trace the trail uphill. The highest point of the staining is the closest thing to the entry you will find from inside, and it tells you which part of the roof to be on. A dark ring on the underside of the deck around a penetration is usually the whole answer.
Then go up and look at that area specifically, and at everything above it on the same slope. Water does not run uphill, so anything downhill of the stain can be ruled out — which is most of the roof. That is why the interior evidence is worth more than a general look over the covering.
Where the attic evidence is thin, a controlled hose test from the bottom of the slope upward, one area at a time, with somebody inside watching. It takes two people and patience. Done casually it floods the attic and proves nothing.
Stopping water versus hiding a stain
A repair that stops water identifies the entry point, corrects the detail that failed, and is documented with a photograph of the thing that was wrong. You can look at the picture and see why the water was getting in.
A repair that hides the stain closes the symptom. Sealant over a suspect area, a patch near the drip, a coat of something across the field of the roof. It buys dry weather, which the next heavy rain takes back.
You can usually tell which you were sold by asking one question: what was the entry point, and where is the picture of it. If the answer is the area above the stain, the leak was not found.
So when we come out to a leak that has already been repaired once, the first thing we want is the attic and the history — not the patch. And if the finding is widespread underlayment failure rather than one detail, we will tell you that straight, with photographs, instead of adding another patch to the roof. Work performed by GenX Roofing LLC, Florida Certified Roofing Contractor, license CCC1333347.