All of a sudden I've noticed that the toilet flapper isn't consistently returning to the closed position. It is fairly new, and I've made some adjustments to the chain, but it is still staying open at least once or twice a day.
What is the flapper catching on that it stays open?
Sometimes the chain has a tendency to kink or tangle after it gets corroded. Here the easiest thing to do is replace the entire flapper.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.