Washing is the key folks, all waterproof, breathable fabrics rely on the outer shell repelling water and the inner coating or membrane providing wicking and breathability.
With most fabrics you must use Nikwax or similar cleaners, or soap flakes! – (except for event which needs to be washed in detergent), and apply a reproofing agent -(again except for event -where heat is most suitable.)
In my experience most jackets that’leak’ are actually wetting out on the outer and then condensating on the inside. Makes sense really – if the outer fabric of your jacket is waterlogged then how can water inside get through it?
Even some ‘new’ jackets can have issues – as many will have been on a slow boat from China for a couple of months, then sat in a warehouse for another month or two, all teh while the DWR can break down – and once that’s gone the jacket ‘wets out’, and you get the breathability issues mentioned above.
i’ve alwasy found Endura kit really good so with the Endura stealth i’d recommend giving it a wash and then maybe a re-proof and then try it again?