Mansfield toilet overflows

I have two new Mansfield toilets; one works fine, the other periodically overflows because the trip lever gets stuck and doesn't drop down. It seems like a simple problem but how do I fix it?

 

A toilet has an opening to the drain, so anything added to it should just go down the drain if it is liquid. A solid might temporarily block it until you had the full force of the tank releasing during a flush, but just a water leak into the bowl would just flow out. So, either the toilet trap or the drain line has to be plugged if it is overflowing.