I have a 2014 329 and it did the same thing. I didn't notice it until I heard a funny noise and looked between the wall and the dinette where the cable runs into the floor. The cage was bent in half where it went through the floor and had broken one section of the plastic cage.
If you look in the outside access door under the dinette, there is a cover with four screws in the upper right hand corner. This is where the cable rolls up when it goes through the floor. When I removed the cover on mine I noticed that the plastic cage was not straight where it was fastened to the inside of the box. This was forcing the cage to go through the hole at a slight angle instead of straight through. It was just enough to cause the cage to bind up when it went thought the hole and eventually break. I bent the connection point just enough to straighten it out and then removed the piece of the plastic cage that was broken. It was long enough that I could remove one section of the cage and it would still work. If you do this make sure you press the round connectors on the plastic into the holes until they "snap" in when you reconnect the cage section. If not the cage will just come apart again (speaking from experience here) After that I sprayed the entire plastic cage with silicone. I ran the slide in and out several times while watching the cage between the wall and the dinette and it didn't bind up. Was going to take it to the dealer but it’s been working fine ever since. I still keep an eye on it when I'm putting the slide out (just in case).
2014 Georgetown 329DS
Towing a 2011 Jeep Wrangler JKU w/ReadyBrake
Yorkie guard dog on the dash