Sorry for the grainy pic, but this is a shot that I took with a snake camera inserted through a ceiling diffuser in my lower level revealing the reason why I've never been able to feel any air flow out of this particular vent Not sure if it was like this since the build in 1996, or if a cleaning done by previous owners could have caused this? Regardless, this connection is roughly 2-3 feet down from the 90 degree elbow that meets the diffuser, so I think I'm going to try removing the diffuser and reaching my arm in there to see if I can grab it. Any other ideas to try to mend this without destroying drywall to access it? This is in the ceiling of a fully finished basement.