For some reason, it will not completely flush all of the waste out with the first flush. Often times it needs to be flushed two or three times.
It seems to be that the flow of water at the end of the flush cycle is somewhat short, hence, not allowing the entire contents of waste to be expelled to the sewer.
The toilet in the other bathroom doen't have a problem.
Our water pressure is not lacking.
The water shut-off valve is open all of the way (that is the first thing that I checked).