I wonder if they made sure the timing was correct, had a good OF valve, governor lever isn't hanging up, or if shutdown lever is coming up all the way, etc. etc. P7100s do fail from time to time but there's a lot of other little things that may not be right. . . and more likely to be the problem. . . than with the P7100 itself.
The real thing to do is if they believe the pump is bad, take it off and have a reputable injection shop TEST it on a stand, instead of simply doing an R&R.
Vaughn