I shoot mine regularly. It loves Federal bulk but not Winchester. When new I did polish the feed ramp and the throat of the barrel. I would not hesitate to get another one.
i would get a ruger mark 3, i like the sig, but there ammo picky, they need mini mag which is hard to get right now, my ruger will shoot anything has a better trigger and is more accurate, my sig dos shoot well if i use mini mag,
Next time you pull the slide off for cleaning, drop a .22 LR round in the chamber. Does it fall in like on a bigger bore auto pistol or hang up partially inserted? Make sure chamber is clean.
I have been shooting my Mosquito for quite a wile and discovered something that may help you if it is not feeding.