It is the second one I purchase and it has the same problem as the previous small one I had. I bought it again in case I had received a defective product, but unfortunately it was not the case.
Inside the plastic parts that snap together, there is a guide. If you don't pay attention and snap it together 100% aligned, it will get stuck. Then, to remove it, you will need a tool and because it is particularly fragile, the guide will break, rendering it useless afterwards as the collar will no longer snap. Unfortunately, it is very easy to snap it incorrectly. The Medium size is much more durable and in the 2 years that I have had it on my dog, it hasn't suffered any damage.