This happened to mine as well, I was a bit disappointed, expect OXO to be better quality. They'd probably replace it if I asked but I feel like it's my fault since I dropped it, even though a plastic cup should survive a fall on the kitchen floor.
It wouldn't surprise me that the plastic had been carefully chosen to lack the plasticity to stay in one piece when dropped from counter-top height; bet that increases profits for the company (at the expense of wasted resources for everyone).
Actually, this wasn't a drop. I had just washed it and was holding it by the handle. I gave it a shake to get rid of the remaining water and it snapped.
I think the joint is somewhat plastic, to the point that it feels slightly flimsy, possibly to prevent drop failure.
This happened to mine as well, I was a bit disappointed, expect OXO to be better quality. They'd probably replace it if I asked but I feel like it's my fault since I dropped it, even though a plastic cup should survive a fall on the kitchen floor.