What the certification does and does not prevent
Gore describes design and garment-construction requirements, including seam sealing and testing. These are manufacturer requirements, not independent comparative evidence that every certified jacket is less likely to leak than an unbranded jacket.
What certification cannot prevent is wear. The garment leaves the factory sealed; ten years of pack straps, cuff flexing, washing and UV act on it afterwards. The guarantee exists precisely because Gore knows the barrier functions can fail in service — its promise is that if they fail within the garment's useful life, it will put things right.
Possible wear and damage
Possible issues include lost DWR repellency, lifting seam tape, abrasion, closure damage and laminate separation. Their timing and order depend on the garment and use; the reviewed sources do not establish a universal lifespan sequence.
Look for lost beading, lifting tape, visible abrasion, separated layers or water near closures. These are clues rather than definitive diagnoses; barrier damage can include membrane failure and should not be dismissed as merely something around it.
Telling a real leak from a saturated face fabric
The field diagnostic is the same as for any waterproof jacket: general clamminess during hard effort is condensation; general wet-out with lost beading is a worn finish; localised, repeatable seepage at one spot is a defect. Gore's own documentation states plainly that a wetted-out face fabric does not mean the membrane is leaking.
If you conclude the defect is real, the guarantee route is the correct one. Gore's published promise covers waterproofness, windproofness and breathability failures for the garment's useful life, with repair, replacement or refund at its discretion. 'Useful life' is Gore's judgement — a heavily worn garment may be deemed at the end of it — but a genuine early defect is exactly what the promise exists for.