The kitty door works just fine. Bo can't fit. The cats can. And, quite honestly, the latch works just fine too...as long as someone locks it.
Sometimes someone forgets to put the latch on the door (we won't get into who). And Bo checks that one door by ramming his head into it. When it has been locked, it sounds like Vikings are taking a battering ram to the house. He grinds his head against the wood, the hinges screech, the door jamb crackles, and the floor rumbles. Cats scatter.
When the door, unlocked and forgotten, has swung open, Bo has entered and has gobbled down all of the dry cat food from the feeder. This snack attack has happened more than once. We won't count.
This act has one significant consequence: Bo gets a tummy ache. Like an old furnace asked to heat ancient pipes for one more winter, Bo whines and groans and rattles around the house for several hours. He requests to go outside...a lot. And he sounds pathetic, but the discomfort and distress eventually passes.
You'd think the humans would remember to keep the door locked!