Subwoofer failure

This morning after everyone was awake I put on Fiona Apple's Tidal record. The very first song, Sleep to Dream has a very loud recurrent low synthesizer note. Everytime it stuck there was a belch in the center field of the system. It turned out to be coming from one of the center subwoofers. These are Dayton Titanic III's and have not been made in years. The current version which uses the same basket has different parameters. Sh-t. 
So, I pulled the driver and sat down with a cup of coffee at the kitchen table with the driver. Everything looked fine and the excursion was smooth and quiet. The surround was in perfect shape as was the spider and lead out wires. Out of frustration thinking I would have to replace all four drivers I started tapping on things. When I tapped on the dust cap I got a mini belch! I ran a finger nail under the seam and sure enough it had detached around 1/3rd of the diameter. I ran a bead of medium viscosity cyanoacrylate glue around the detached area and it sucked it right up. Driver reinstalled it was back to normal. 
Subwoofer drivers have a very aggressive lifestyle and they can fail in many ways that can be easily fixed. This is just one example we can store in memory. 
Anybody else have a subwoofer driver failure?