It’s either a bad o-ring or something like a pine needle is stopping it from fully closing.
Take the filter apart and see if you can find anything blocked up in the release pipe.
pre-pandemic I had a similar issue with mine and a whole new one with the gauge was $37 so I ordered it without even looking. When I had time to swap it, It was jam clogged with pool brush bristles. I needed the gauge anyway so I just kept the old valve as a spare.
It should just be a big plastic nut under the filter top (with a gasket there too). Take the filter apart, Unscrew the valve and check first for anything stuck up in there. If it’s all clean look up the parts diagram on inyopools. You should be able to buy the pieces (the gasket for the twisty part). If not buy the whole thing.