If it has an electric coil operated cartrage type shut off near or on the pump, pull the cartrage out and look at the O rings for damage. Sounds like it dribbles like when you think your done peeing and you reel it on in and your glad your’re wearing your shorts.
Bad O rings is like the valve not being shut off all the way. Valve seat bad or spool rod stuck...same thing.
Some nozzle atomizor tips also have check valve to shut off the drip.
My experiencd is on construction heaters ...big and small.
I’m an all around mechanic, very dangerous to be one.
" It was later determined that two rubber O-rings, which had been designed to separate the sections of the rocket booster, had failed due to cold temperatures on the morning of the launch. The tragedy and its aftermath received extensive media coverage and prompted NASA to temporarily suspend all shuttle missions."