The Chinese artisans who hand-carve every single one of these ceramic inserts from a solid block of ceramic work incredibly hard, so sometimes they’re given the day off. And while they take a break, their children take over - and sadly the kids’ work is often not quite up to the standard of their parents.
The good thing is that if you report this carving error to your TD, they’ll remove the insert and check the ID number on the back that identifies which worker carved it - and the guilty party will be executed. It sounds harsh, but it means there’s much less chance of the same terrible flaw being repeated again. So don’t feel too bad about it.