At the Canadian Grand Prix on Saturday, Di Resta again rounded on the team after another mistake compromised his qualifying for a second successive race.
An error in Monaco a fortnight previously had resulted in the Scot starting from 17th, describing the situation afterwards as "probably the most painful experience I've ever had in qualifying".
In Montreal, Di Resta again failed to make it out of Q1, repeating his 17th place on the grid following which he said: "It's the fault of the team again and it's just not good enough."
Come the races, however, Di Resta underlined his growing form and status by finishing ninth in Monaco and seventh in Montreal to push him up to eighth in the drivers' standings.
Despite Di Resta's abrasive comments, Fernley has no qualms with Di Resta letting rip as he told Press Association Sport: "What he said probably came across worse than it actually was.
"We don't take offence the way people may think we do because we know him and he is a part of our family.
"With Paul, what you see is what you get. He wears his heart on his sleeve, and when he's not happy, you know he's not happy.
"But on a day-to-day basis he is a delight to work with, and he's just as hard on himself as he is on anybody else because he's looking for perfection all the time."
Di Resta's frustration is down to the fact the car Force India has produced this season is a consistent top-10 contender in both qualifying and the race.
Appreciating the situation, Fernley conceded: "Yes, there was a genuine error by the team in the garage that cost him a lap.
"Unfortunately it was compounded by the fact that on one of the laps on which he was trying to get a time, (Nico) Rosberg spun in front of him.
"In his mind, had he had one more lap he would have been okay, but we don't know that. We just have to deal with these things in what were very difficult circumstances."
Overall, Fernley could not be happier with the way Di Resta has been performing this season, adding: "He is driving exceptionally well.
"I watched him on Friday (in practice) and it was an absolute pleasure to see him and the team working together the way they did.
"There were some five-lap runs which were sensational, absolutely sensational.
"On Saturday we unfortunately took a step back, but in the race we delivered again, so yes, he is really on top of his game at the moment."