sammiekat, your post had me wondering about all of my Chanel bags chain links and lo and behold, after checking each bag, found that all four links on my beloved black deerskin Luxury bowler have these separations as well. They are much smaller separations than on your Cabas but darn, for the price I paid, I expect Chanel to have soldered them closed! And because the links are not as thick as the the Cabas I worry they could open up. I've had my bowler since last August and although it isn't an everyday bag, I haven't babied it when in use.
I still think you are making the right decision though since the openings on your links look quite large and while they probably won't open further, it looks like the leather piece could slip through. And, your mind will never rest when carrying the bag, always wondering if the chain will break.
I would try to find another and ask the s/a to check the links before sending it to you.