A gasket that fails at the same joint twice is telling you something specific, and it is not about the gasket. One made of the wrong material fails across its whole face: it hardens, it crumbles, it cracks along the hottest part of the bore. A gasket pushed out at one point on the perimeter is being extruded, and extrusion needs a gap. The gap is the fault.
The second failure also carries information in its timing. If it went sooner than the first, the joint never changed and the gap was never closed. If it lasted about as long, the gap is opening under thermal movement rather than being present from the day it was assembled.
Most exhaust joint gaskets do not seal by being squeezed into something soft. They seal because bolt load compresses the material against two flat faces and it fills the small irregularities in those faces. The seal depends on that load reaching the gasket evenly around the perimeter, and on the gasket being confined so it cannot escape sideways.
Both conditions are easy to lose. If one side of the pair is stiffer, or the fasteners sit closer together on one side, load concentrates and the far edge gets very little. If the faces are not parallel, the joint closes first at the stiffest point and stays open elsewhere.
Once the joint opens locally, gas pressure and thermal cycling work on the exposed edge on every drive. It erodes from that edge inward, and the damage looks like a bite taken out of one side rather than a worn face. On a joint with a bore step the mechanism runs in reverse: part of the gasket has nothing behind it and is drawn into the pipe.
So the first question with the joint apart is not what the middle of the gasket looks like. It is where on the perimeter the damage starts, and whether that point had an unsupported edge behind it.
The most common is a flange distorted by welding. A plate welded to tube pulls as the weld cools, and a flat plate pulls into a shallow cone. The face still looks flat to the eye and reads flat against a rule held one way, but the pair now touches at the outside edge and stands open at the bore. The gasket is clamped on a narrow ring.
The second is alignment. If the sections either side do not share an axis, tightening the joint bends the assembly and the pair takes a hinge load. The third is a step: a bore mismatch, a burr, or a bead left proud. The fourth is a joint with no support near it, so the assembly moves and works the gasket rather than the hanger.
Clean both faces and bolt them together dry, with no gasket, then take a feeler gauge around the perimeter. If it enters at one point and not the others, the faces are not parallel and the joint is a hinge. A straight edge across each face in two directions shows a cone that a single reading hides.
Then check the bore. Run a finger around the inside of the joint; a lip or step is easy to feel and hard to see. Make sure the fasteners are not bottoming in their threads before the faces meet, which mimics a soft gasket. Finally look at what holds the joint in space. A flange with no hanger within reach is a flange that flexes.
If the flange is conical, replace it or face it flat, and check it flat after welding rather than before. If the faces are parallel but the joint is loaded, correct the alignment so it closes without being pulled, and add support near the joint. If the bore has a step, machine it out or use a gasket supported across its full face.
Only then fit a gasket, and fit the one the joint was designed for. A thick soft gasket will hide a small gap for a while, which is worse than failing immediately, because it turns a fit problem into a recurring one. On any stainless steel exhaust system the flanges and the support decide whether the joint stays closed.
