You have to hold your nose and have a bucket there and open the valve. Spray the heck out of it all with silicone spray and work the valve open and closed a lot till you are happy. If not happy, replace the valve.
We had a the black valve handle come right out one time like that, where the other end had parted somewhere inside under (above) the underbelly. Lucky for us, it was a warranty item. The dealer techs did not enjoy that job. That was years ago, and I am waiting for it to happen again so it will be my turn to fix it. :(
I have another knife valve I put in at the sani-dump end and it responds to silicone spray like magic. Same with the cap for getting it on and off easily.
