This hole was the problem.
Someone had cut a hole in the gate so this wheel could swivel.
Consider It Done Construction re-engineered the gate, and closed the hole in the gate so the owner's dog wouldn't get loose.
This is what the back of the gate looked like before the repairs.
With the addition of this little wheel on the post of the gate, the hole was no longer necessary, and the gate opens and closes smoothly.
Problem. Solved.
Problem. Solved.