Sims finished a solid 12th in the first of the two races at Rome's Circuito Cittadino dell'EUR circuit, and was once again in the midfield before a lock-up while trying to pass Nissan's Maximilian Guenther at Turn 14 put him into the wall in the second contest.
Although Sims explained that the pace "didn't feel too terrible", where the Briton had put together a series of good laps in the early stages, he added he was lacking confidence in the overall package and didn't foresee an immediate fix to his problems.
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"I don't have any clear, specific things that I can see a huge improvement coming from, I'm a little bit lost and lacking in confidence at the moment," Sims told Autosport.
"We need to just try and understand where some of that is coming from and just try and make those incremental improvements as it normally is.
"There's rarely one massive single moment that can suddenly change your fortunes entirely. So it's hard work at the moment."
Sims explained the team struggled in particular with qualifying pace, and called upon that to be Mahindra's main focus as it heads into the Monaco round at the end of the month.
He added that the second Rome race was "tough to read", and believes most of the cars around him were saving energy heavily in the opening stages; having felt he was doing a good job to conserve his own useable energy, Sims was surprised to hear he was "in the mix" with his rivals.
"It didn't feel like our pace was too terrible," Sims continued. "It was tough to really read what was happening in the race. But it seemed everyone was saving a lot.
"Even though I felt I was doing a good job in energy, my engineer was saying I was in the mix with everyone else, a bit up on some and a bit down on others. Everyone must have just been in saving mode around me.
"We'd just taken attack when I then had my crash. I was sort of hoping to be able to make hay while the sun shone with the extra power and pull myself back through the field.
"The race pace was not horrendous; to be honest, it's probably the strongest point of the weekend. Our qualifying placement, for me particularly was very poor. So that's really got to be the main focus I think."
