Sounds like the dust filter disintegrated, and got into the gap. That would cause that obstructed movement. You'll have to remove the cone and clean out the vc gap. Better to remove it as a unit. With some ingenuity you won't have to remove the dust cap in order to shim it during re install. MEK is the product to remove the spider and surround. Sparingly brush on a thin layer and wait 5-10 min. You may have to repeat as required(better to not overdo). Gently pull off the surround and spider making sure you don't pull off the tinsels. They can be unscrewed once you turn the freed cone out of the way. The MEK will simply evaporate in about a 24hr period to be safe. "Safe" is the operative with MEK as it's deadly. Make sure you either do it outside or with serious ventilation. You can re shim with narrow strips and spot glue the spider to re center the vc for re install, then pull them out and glue down the remainder of the spider, then surround. Gently does it. Done!
simple.