Wow, LMB did a good job! w/ that being said, I would have been polite yet stern at the SA and tell her since it's only been 4 mo and carried a few time that it could not be wear and tear but defect. Bec. if it's wear and tear what does that say about LV quality??? and that you want to leave your bag to them for a free repair. JMO
All SA will tell you it's normal wear and tear if you bring up a problem to them. When my Ebene Alma was about a year old, I noticed there was a hairline crack on the keybell holder I showed it to them and they told me it's normal wear and tear and I told the SA no bec. I only carried it a few times and before the problem gets worse I want it replaced. She accepted that and ordered me a new keybell holder free of charge.
Again though, LMB did a great job and I'm glad all worked out ok for you in the end