You should have some suction, just not a lot.
Also, you know the ccv is right behind the disa, and it wouldn't surprise me if it does buzz when it's failed a certain way. It makes a chewbacca noise, why not buzzing?
Just doublecheck your assumptions before you buy a disa. I know they fail, but I also know mine hasn't...though my and everyone else's ccv has failed after so many miles.
I wish there was a better test for ccv failure than the sucking bag!