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?
Sometimes a new lever helps, if the one you have is sticking.
Overflowing the bowl? That would mean the bowl is plugged.
Using a plunger or closet auger can help with that, though the builder grade Mansfield Alto model is not one I recommend. We remove and dispose of those all the time.
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.